thanks for the compliments, but felt it could be improved further especially the hydrogen alpha luminance component. I have redone this component again. you can view the smaller version here and a higher resolution over here:
http://www.geocities.com/remuscj/imaged ... naeHaL.jpg
H-Alpha Imaging
Remus,
This is a very impressive image. Especially since it was taken from Singapore. Comparing your image to mine, yours have much more detail.
Since you have taken yours with Ha filter, I was thinking that it may be time I'll get one myself. Do you think that it will work for DSLR? I was thinking of taking a Ha frame and combined with another one without.
I don't really like the idea of taking four images for each filter with a CCD camera. If yes, what is a good Ha filter to buy?
Hope this is not consider off topic.
Thanks,
CK
This is a very impressive image. Especially since it was taken from Singapore. Comparing your image to mine, yours have much more detail.
Since you have taken yours with Ha filter, I was thinking that it may be time I'll get one myself. Do you think that it will work for DSLR? I was thinking of taking a Ha frame and combined with another one without.
I don't really like the idea of taking four images for each filter with a CCD camera. If yes, what is a good Ha filter to buy?
Hope this is not consider off topic.
Thanks,
CK
Hi Perseid,
Yes you can certainly embark on DSLR H-alpha imaging. Infact, some years back, I have tried using Lumicon's H-alpha deep sky filter with a nikon 50mm lens and nikon SLR to take Cygnus region. The H-alpha filter certainly helped to bring out the nebulosities in Veil, Gamma Cygni and NGC700 complex, and we could see all that even at 50mm image scale.
What are you planning to use as the optical instrument with the DSLR?
I am asking because if you plan on using a telephoto lens, then perhaps you could get a frontal lens H-alpha filter for this purpose. If you are planning to shoot through an OTA, then perhaps you need to get the filter to insert in between the DSLR and OTA, which means you should try to have a big enough filter to avoid vignetting issues.
The H-alpha filter that was used to take the Eta C image was actually purchased solely for CCD imaging in mind, and is a 1.25" version placed in the motorised filter wheel. Filters used for DSLRs are normally bigger in diameter and more $$$. However there are low cost H-alpha filters in the market that cost lesser and are actually photographic deep red filter like the Kenko R64 deep red filter series ranging from 52 to 77mm in diameter. The cost is definitely below S$100. You could try Lumicon's as well, but will be more expensive, but they work well. For CCD imaging, for your reference, imagers use brands ranging from Astronomik, Custom Scientific, etc..but comes in 1.25" and 2" sizes (though custom sizes might be possible). Also, H-alpha narrowband filters come in various passband widths. The smaller the width, the more "accurate" is the capture of emission nebulae and you will have generally bigger star diameters since the filter allows more light to pass through. Smaller passband widths filters will ensure better production "accuracy" in emission nebulae structure but at the consequence of dimmer and smaller stars since lesser light passes through.
As for the thoughts about taking multiple filtered components using a CCD, at first I thought it was pretty troublesome to do that too, and takes up more time, but according to CCD imagers, the colours rendered in this case is much richer and more contrasty than single shot imaging devices. But of course, it is also a more costly approach as well. For DSLR, you could achieve close to rich colour as much as possible by imaging in darker sites (which you have) and taking more and longer stacks.
2 cents!
Yes you can certainly embark on DSLR H-alpha imaging. Infact, some years back, I have tried using Lumicon's H-alpha deep sky filter with a nikon 50mm lens and nikon SLR to take Cygnus region. The H-alpha filter certainly helped to bring out the nebulosities in Veil, Gamma Cygni and NGC700 complex, and we could see all that even at 50mm image scale.
What are you planning to use as the optical instrument with the DSLR?
I am asking because if you plan on using a telephoto lens, then perhaps you could get a frontal lens H-alpha filter for this purpose. If you are planning to shoot through an OTA, then perhaps you need to get the filter to insert in between the DSLR and OTA, which means you should try to have a big enough filter to avoid vignetting issues.
The H-alpha filter that was used to take the Eta C image was actually purchased solely for CCD imaging in mind, and is a 1.25" version placed in the motorised filter wheel. Filters used for DSLRs are normally bigger in diameter and more $$$. However there are low cost H-alpha filters in the market that cost lesser and are actually photographic deep red filter like the Kenko R64 deep red filter series ranging from 52 to 77mm in diameter. The cost is definitely below S$100. You could try Lumicon's as well, but will be more expensive, but they work well. For CCD imaging, for your reference, imagers use brands ranging from Astronomik, Custom Scientific, etc..but comes in 1.25" and 2" sizes (though custom sizes might be possible). Also, H-alpha narrowband filters come in various passband widths. The smaller the width, the more "accurate" is the capture of emission nebulae and you will have generally bigger star diameters since the filter allows more light to pass through. Smaller passband widths filters will ensure better production "accuracy" in emission nebulae structure but at the consequence of dimmer and smaller stars since lesser light passes through.
As for the thoughts about taking multiple filtered components using a CCD, at first I thought it was pretty troublesome to do that too, and takes up more time, but according to CCD imagers, the colours rendered in this case is much richer and more contrasty than single shot imaging devices. But of course, it is also a more costly approach as well. For DSLR, you could achieve close to rich colour as much as possible by imaging in darker sites (which you have) and taking more and longer stacks.
2 cents!
Remus,
Thank you very much for your explanation.
Yes, I agree that images taken with CCD through various RGB filter will bring out the colour well. However, I have tried this method and failed on many occasions. The problem I faced constantly was bad weather, misalignment between various colour images and not enough exposure on certain colour, especially the green. Another thing I don't like about CCD is that the sensor is very small. Very difficult to do guiding and low in resolution. (can't afford those mouth-watering mount with low PE). That is the reason I currently stick to DSLR. And I will try to stay away from RGB imaging with CCD for now.
But now, I am eager to try Ha. I will probably use an OTA (100mm ED) for this imaging, so I guess a two inch filter is recommended? I am currently using a 100mm F9 with a 6.3 reducer. As such I was thinking of making a thread so that the filter can screw to the reducer. So the arrangement would be OTA, filter, reducer, camera. Would this work? With this, I don't think a narrow band Ha would work because of the faster configuration.
Since you have used both DSLR and CCD, which do you prefer?
Thank you very much for your explanation.
Yes, I agree that images taken with CCD through various RGB filter will bring out the colour well. However, I have tried this method and failed on many occasions. The problem I faced constantly was bad weather, misalignment between various colour images and not enough exposure on certain colour, especially the green. Another thing I don't like about CCD is that the sensor is very small. Very difficult to do guiding and low in resolution. (can't afford those mouth-watering mount with low PE). That is the reason I currently stick to DSLR. And I will try to stay away from RGB imaging with CCD for now.
But now, I am eager to try Ha. I will probably use an OTA (100mm ED) for this imaging, so I guess a two inch filter is recommended? I am currently using a 100mm F9 with a 6.3 reducer. As such I was thinking of making a thread so that the filter can screw to the reducer. So the arrangement would be OTA, filter, reducer, camera. Would this work? With this, I don't think a narrow band Ha would work because of the faster configuration.
Since you have used both DSLR and CCD, which do you prefer?
Hi Perseid,
Hmm...I understand your situation. In fact, I faced the same things that you did with CCD imaging as well. The recent image was certainly attributed to being in luck with intermittently good weather for a good few hours, enough to take an image to see that everything works fine. I have learnt to try to take the RGB components all at one go consecutively, instead of on different nights with the same object for fear of too much of a misalignment. Which software did you use for alignment the other time? You could try IRIS if you didn't, it will do the job nicely. The big boys normally use Registar but the price tag of USD$149 just for a piece of registration software does not make sense to me! Also, in RGB imaging, you need to find out the individual RGB imaging ratios first and do a G2V star calibration so that your star colours will be balanced. I have issues with the green channel as well...particularly more noise comes from there, so I had to smooth the channel more, but at the same time retain the sharpness profile of the stars.
Actually, with the recent advances in DSLR imaging, one can do pretty decent work in this field as well, and yes, nothing beats the convenience of shooting RGB all at once. I hear that the recent D50 from Nikon may have even lower noise characteristics than some cooled CCDs!
Personally though, I have not even gotten to modifying the D70 that I have for emission imaging. Most of the imaging done with it is for the moon, sun and clusters like Omega Centauri. I have done an Orion Nebula, but don really like the way the colours turned out. You have done the modifications already, and like you'd said during the convention, the h-alpha component is much more.
I would also advise that you should get a 50.8mm HA filter instead. The sequence should be okay for your configuration stated, but am curious to know how does effective focal ratio got to do with whether the narrowband HA will work?
Lastly, as to which medium do I prefer, both have its pros and cons, so it depends on the situation that I am in at hand. DSLR is good for the convenience and the fact that you don't have to spend additional time taking separate RGB components especially in places where good weather is hard to come by. You do not need as much power outfield to power the DSLR as compared to a 2A/hr astronomical CCD camera.
CCD imaging on the other hand definitely requires a laptop as well capturing, need more power and more time to acquire all the individual channel components if you decide to go for hybrid colour imaging. However, I like how the stars look in the CCD, a little more 3 dimensional, and I could image at a definitive temperature (like 0 degrees), which yields more accurate darks for image calibration. And better colour.
On a personal note, frankly, I am quite impressed with H-alpha imaging in general whether it would be DSLR or CCD form in narrowband terms (>13nm), especially capturing all the wispy filamentary structures and bok globules, and will probably look attractive as a single Ha component itself, even without the need to shoot RGB.
A thing to note when shooting H-Alpha, it is best to find the object first using no filter for composition, since taking deep red is going to cut down a lot on star light! You will also got to prepare yourself for different star sizes of the H-alpha (much smaller) than the accompanying colour RGB component. But when you come to that situation and have not figured out how to resolve the differing star sizes, let me know! ;P
Hmm...I understand your situation. In fact, I faced the same things that you did with CCD imaging as well. The recent image was certainly attributed to being in luck with intermittently good weather for a good few hours, enough to take an image to see that everything works fine. I have learnt to try to take the RGB components all at one go consecutively, instead of on different nights with the same object for fear of too much of a misalignment. Which software did you use for alignment the other time? You could try IRIS if you didn't, it will do the job nicely. The big boys normally use Registar but the price tag of USD$149 just for a piece of registration software does not make sense to me! Also, in RGB imaging, you need to find out the individual RGB imaging ratios first and do a G2V star calibration so that your star colours will be balanced. I have issues with the green channel as well...particularly more noise comes from there, so I had to smooth the channel more, but at the same time retain the sharpness profile of the stars.
Actually, with the recent advances in DSLR imaging, one can do pretty decent work in this field as well, and yes, nothing beats the convenience of shooting RGB all at once. I hear that the recent D50 from Nikon may have even lower noise characteristics than some cooled CCDs!
Personally though, I have not even gotten to modifying the D70 that I have for emission imaging. Most of the imaging done with it is for the moon, sun and clusters like Omega Centauri. I have done an Orion Nebula, but don really like the way the colours turned out. You have done the modifications already, and like you'd said during the convention, the h-alpha component is much more.
I would also advise that you should get a 50.8mm HA filter instead. The sequence should be okay for your configuration stated, but am curious to know how does effective focal ratio got to do with whether the narrowband HA will work?
Lastly, as to which medium do I prefer, both have its pros and cons, so it depends on the situation that I am in at hand. DSLR is good for the convenience and the fact that you don't have to spend additional time taking separate RGB components especially in places where good weather is hard to come by. You do not need as much power outfield to power the DSLR as compared to a 2A/hr astronomical CCD camera.
CCD imaging on the other hand definitely requires a laptop as well capturing, need more power and more time to acquire all the individual channel components if you decide to go for hybrid colour imaging. However, I like how the stars look in the CCD, a little more 3 dimensional, and I could image at a definitive temperature (like 0 degrees), which yields more accurate darks for image calibration. And better colour.
On a personal note, frankly, I am quite impressed with H-alpha imaging in general whether it would be DSLR or CCD form in narrowband terms (>13nm), especially capturing all the wispy filamentary structures and bok globules, and will probably look attractive as a single Ha component itself, even without the need to shoot RGB.
A thing to note when shooting H-Alpha, it is best to find the object first using no filter for composition, since taking deep red is going to cut down a lot on star light! You will also got to prepare yourself for different star sizes of the H-alpha (much smaller) than the accompanying colour RGB component. But when you come to that situation and have not figured out how to resolve the differing star sizes, let me know! ;P
i think i may have just thought of an answer to the question i posted on the earlier post, perseid.
For narrower passband H-alpha filters, there is a trade off when using at higher focal ratios, which include the slight shift in the filter passband due to change in angle of incidence which is a greater factor for fast telescopes and further accentuated with bigger chip sizes.
I guess ultimately, the choice of a passbandwidth for H-alpha imaging will thus depend on sky conditions, the kind of object to be imaged (whether you are imaging a solely HII emissive nebula like Eta Carinae, or a mixed emission nebula like Orion Nebula), and the question of whether you want to allow admitting more starlight or not. This is because purists of H-alpha imaging may also argue that if one were to embark in H-alpha imaging, it is essentially a narrowband activity, otherwise the effectiveness in capturing the HII regions purely, will be lost. But I think I would understand your situation in the sense that even a broader passband H-alpha would complement the red channel of the RGB component much better and yield richer HII tonality in resulting images.
BTW, I have forgot to mention that Baader also makes H-alpha filters featuring broader passbands (45nm), and features good anti-reflective coatings as well.
For narrower passband H-alpha filters, there is a trade off when using at higher focal ratios, which include the slight shift in the filter passband due to change in angle of incidence which is a greater factor for fast telescopes and further accentuated with bigger chip sizes.
I guess ultimately, the choice of a passbandwidth for H-alpha imaging will thus depend on sky conditions, the kind of object to be imaged (whether you are imaging a solely HII emissive nebula like Eta Carinae, or a mixed emission nebula like Orion Nebula), and the question of whether you want to allow admitting more starlight or not. This is because purists of H-alpha imaging may also argue that if one were to embark in H-alpha imaging, it is essentially a narrowband activity, otherwise the effectiveness in capturing the HII regions purely, will be lost. But I think I would understand your situation in the sense that even a broader passband H-alpha would complement the red channel of the RGB component much better and yield richer HII tonality in resulting images.
BTW, I have forgot to mention that Baader also makes H-alpha filters featuring broader passbands (45nm), and features good anti-reflective coatings as well.
Remus,
Previously, I use Astroart 2.0 to do the RGB processing. That was about four years ago. I think I'll give IRIS a try. I have not learn to use it extensively yet.
One of the other reason why I am using DSLR is that I found that the faintest star that I'm able to record on a DSLR is quite close to the cooled CCD for similar exposure time. Judging on the convenience of setting up, I prefer DSLR to CCD. I have not seen people taking narrowband imaging using DSLR. If it is doable, then I'll definitely stick to DSLR for quite a while.
As for the Baader broadband Ha (45nm), don't you think that the image will be "contaminated" with SII line? I noticed that some manufacturer offer Ha filter which look like a long wave pass filter (transmission begin before Ha and go way beyond to IR range). What's your opinion on these filters?
Previously, I use Astroart 2.0 to do the RGB processing. That was about four years ago. I think I'll give IRIS a try. I have not learn to use it extensively yet.
One of the other reason why I am using DSLR is that I found that the faintest star that I'm able to record on a DSLR is quite close to the cooled CCD for similar exposure time. Judging on the convenience of setting up, I prefer DSLR to CCD. I have not seen people taking narrowband imaging using DSLR. If it is doable, then I'll definitely stick to DSLR for quite a while.
As for the Baader broadband Ha (45nm), don't you think that the image will be "contaminated" with SII line? I noticed that some manufacturer offer Ha filter which look like a long wave pass filter (transmission begin before Ha and go way beyond to IR range). What's your opinion on these filters?
If I may OT from the discussion a little, not for the benefit of CK (whom has deeper knowledge of filter design than I do) but mainly for those interested.
To attain high resolution imaging like what Remus did, there are three other important factors to consider, before commitment to any exotic and pricey H-alpha filter. They are IMHO;
1. Autoguiding
2. Monochrome sensor.
3. Sensitivity.
1. ST2000 has a built-in AG chip, when engaged; maintain mount tracking to single digit arcsecond accuracy. This assures pinpoint stars and mitigates image blurring. Fortunately autoguiding is not exclusive to SBIG cameras and can be accomplished by much more affordable means.
For H-Alpha imaging, exposure duration for each subframe needs to be considerably longer due to the limited spectrum of photons. Hence autoguiding at longer focal length (say >300mm) becomes not a luxury but a necessity.
2. ST2000 adopts a monochrome Kodak 2-Megapixel KAI-2001M CCD as it main imaging chip. (Chip Size 13.38mm (H) x 9.52mm (V))
Where as all modern DSLR (modified or not) boast at least 4x the sensor area size to the former! But all these DLSR sensors sport a layer of bayer filter matrix, which further reduces native resolution - call it a necessary evil. It does this by recombining bayer filtered pixels (RGGB) and averaging neighboring pixels arrays to form a smooth transition of colours that appeals to average consumers in colours.
FAQ on bayer filter can be found here
http://www.cs.duke.edu/~parr/photography/faq.html#bayer
Contrary to what many believe, Nyquist rule of thumb for 2 arcsecond/pixel sampling does not hold well for DSLR, for its apparent pixel is usually larger than it native pixel (6-8um).
Imagine if a monochrome sensor uses each pixel to present spectral information. A DSLR OTOH uses at least 4X the pixels (RGGB) to derive a spot of color info and does this with a lot interpolation (IOW: guess work). You can easily guess which will yield a higher resolution.
I am not sure the day will come when DSLR manufacturers starts selling monochrome camera with a full frame or 1.6 cropped factor sensor.
3. Using dedicated H-alpha filter, a monochrome CCD uses all it pixels to collect spectral infomation in 636.5nm band and does so in comparitively good efficiency. Where as a DSLR uses only ¼ of the available pixels (Red of RGGB) for H-alpha, so when it comes sensitivity, the a/m factor culiminate into an uphill task for the modified DSLR to match the former, let alone the stock DSLR, H-alpha imaging is not worth attempting.
The main advantage of DSLR has two unbeatable attribute though – cost & conveneince. And since CK has a pretty good DSLR considering that it has been modified. My personal choice would be to partner the broader but affordable Baader 2” 45nm H-alpha with DSLR while reserving the sub 10nm bandpass for a monochrome CCD.
Happy imaging
Matthew
To attain high resolution imaging like what Remus did, there are three other important factors to consider, before commitment to any exotic and pricey H-alpha filter. They are IMHO;
1. Autoguiding
2. Monochrome sensor.
3. Sensitivity.
1. ST2000 has a built-in AG chip, when engaged; maintain mount tracking to single digit arcsecond accuracy. This assures pinpoint stars and mitigates image blurring. Fortunately autoguiding is not exclusive to SBIG cameras and can be accomplished by much more affordable means.
For H-Alpha imaging, exposure duration for each subframe needs to be considerably longer due to the limited spectrum of photons. Hence autoguiding at longer focal length (say >300mm) becomes not a luxury but a necessity.
2. ST2000 adopts a monochrome Kodak 2-Megapixel KAI-2001M CCD as it main imaging chip. (Chip Size 13.38mm (H) x 9.52mm (V))
Where as all modern DSLR (modified or not) boast at least 4x the sensor area size to the former! But all these DLSR sensors sport a layer of bayer filter matrix, which further reduces native resolution - call it a necessary evil. It does this by recombining bayer filtered pixels (RGGB) and averaging neighboring pixels arrays to form a smooth transition of colours that appeals to average consumers in colours.
FAQ on bayer filter can be found here
http://www.cs.duke.edu/~parr/photography/faq.html#bayer
Contrary to what many believe, Nyquist rule of thumb for 2 arcsecond/pixel sampling does not hold well for DSLR, for its apparent pixel is usually larger than it native pixel (6-8um).
Imagine if a monochrome sensor uses each pixel to present spectral information. A DSLR OTOH uses at least 4X the pixels (RGGB) to derive a spot of color info and does this with a lot interpolation (IOW: guess work). You can easily guess which will yield a higher resolution.
I am not sure the day will come when DSLR manufacturers starts selling monochrome camera with a full frame or 1.6 cropped factor sensor.
3. Using dedicated H-alpha filter, a monochrome CCD uses all it pixels to collect spectral infomation in 636.5nm band and does so in comparitively good efficiency. Where as a DSLR uses only ¼ of the available pixels (Red of RGGB) for H-alpha, so when it comes sensitivity, the a/m factor culiminate into an uphill task for the modified DSLR to match the former, let alone the stock DSLR, H-alpha imaging is not worth attempting.
The main advantage of DSLR has two unbeatable attribute though – cost & conveneince. And since CK has a pretty good DSLR considering that it has been modified. My personal choice would be to partner the broader but affordable Baader 2” 45nm H-alpha with DSLR while reserving the sub 10nm bandpass for a monochrome CCD.
Happy imaging
Matthew
Hi perseid,
my point exactly...if you are committing to broader bandpass HA filters, you will be doing something contrary to the purpose of obtaining true HII regions that a narrowband filter can effectively do. But there are still people out there that have done H-alpha imaging using DSLRs, but not as a dormant imaging project unlike the numerous H-alpha projects that monochrome CCD imagers embark on. As Matthew has iterated, you have to accept the apparent lost effective resolution due to the Bayer configuration. Actually there are some cheaper CCD alternatives there like the Artemis range (just a little more expensive than a DSLR) and the Starlight Xpress, all utilises the low noise sony chips.
As for software use, IRIS, no doubt an apparent initial steep learning curve that it is, it very effective in image processing, and with a whole lot of important features that it has, and all for zero cost. Personally, I also find myself slowly weaning off away from Photoshop more and more, leaving it to use in only the final touches. Stacking, colour combine, and other sharpening functions can be done in IRIS. There are also other software packages out there like ImagePlus, MaxIM DL, CCDSoft, AIP4WIN, and is worthy of consideration, but you have to be prepared to spend for these premiere software. IRIS comes close.
Lastly, pertaining to set up time, I guess it is really up to the individual. The more you practise and am familar with the equipment set up process, the more efficient and faster you will get to capturing your first image.
It is seriously not too difficult or tedious nowadays as the process basically involves the same number of steps whether DSLR or CCD, just that CCD has an additional step that requires the need to calibrate the mount for autoguiding. But if you are using a webcam for guiding with your DSLR for example, you cannot skip this step too right?
For those interested in the preliminary procedures before capturing, this is currently what I do for the CCD session:
1) Set up the GEM, connect electronics, mount up OTA
2) Set up CCD connection to laptop and mount
3) Drift alignment with reticle eyepiece
4) Image composition (decide what you want to capture)
5) Center the object in the CCD chip, and start focusing
6) Activate the CCD software to calibrate the mount for purposes of autoguiding
7) Start the autoguider, let it guide for a while, and allow the mount to "stabilise" to guiding
8) Start exposure
9) You can start doing your own things while the system captures for you, be it a couple of exposures, or different colour components.
Depending on how familar you are with the system, you can do the above steps within an hour or even shorter.
my point exactly...if you are committing to broader bandpass HA filters, you will be doing something contrary to the purpose of obtaining true HII regions that a narrowband filter can effectively do. But there are still people out there that have done H-alpha imaging using DSLRs, but not as a dormant imaging project unlike the numerous H-alpha projects that monochrome CCD imagers embark on. As Matthew has iterated, you have to accept the apparent lost effective resolution due to the Bayer configuration. Actually there are some cheaper CCD alternatives there like the Artemis range (just a little more expensive than a DSLR) and the Starlight Xpress, all utilises the low noise sony chips.
As for software use, IRIS, no doubt an apparent initial steep learning curve that it is, it very effective in image processing, and with a whole lot of important features that it has, and all for zero cost. Personally, I also find myself slowly weaning off away from Photoshop more and more, leaving it to use in only the final touches. Stacking, colour combine, and other sharpening functions can be done in IRIS. There are also other software packages out there like ImagePlus, MaxIM DL, CCDSoft, AIP4WIN, and is worthy of consideration, but you have to be prepared to spend for these premiere software. IRIS comes close.
Lastly, pertaining to set up time, I guess it is really up to the individual. The more you practise and am familar with the equipment set up process, the more efficient and faster you will get to capturing your first image.
It is seriously not too difficult or tedious nowadays as the process basically involves the same number of steps whether DSLR or CCD, just that CCD has an additional step that requires the need to calibrate the mount for autoguiding. But if you are using a webcam for guiding with your DSLR for example, you cannot skip this step too right?
For those interested in the preliminary procedures before capturing, this is currently what I do for the CCD session:
1) Set up the GEM, connect electronics, mount up OTA
2) Set up CCD connection to laptop and mount
3) Drift alignment with reticle eyepiece
4) Image composition (decide what you want to capture)
5) Center the object in the CCD chip, and start focusing
6) Activate the CCD software to calibrate the mount for purposes of autoguiding
7) Start the autoguider, let it guide for a while, and allow the mount to "stabilise" to guiding
8) Start exposure
9) You can start doing your own things while the system captures for you, be it a couple of exposures, or different colour components.
Depending on how familar you are with the system, you can do the above steps within an hour or even shorter.
Hi CK,
What about this one?
http://www.icas.to/space/Digital-camera ... igital.htm
At 500++ SGD, it ought to be the most expensive dustcover ever built.
Let me know if you have the facilities to prototype this glass. I am hoping Anat might be brewing something along this line too.
You are correct to say some H-alpha (such as Kenko, Lumicon) are long pass filters that extend to NIR. This LP can be work around if you stack an hot mirror which form a H-Alpha & SII bandpass, provided if you already have access to these combination. Otherwise 2” 45nm Ha may not be such a bad choice.
Admittedly, I have not considered the effect of SII “contamination” yet. More often than not, there are other mysterious factors that conspire to wreck my H-Alpha imaging attempts before SII does. These are just some issues we’ve got to live with without the comfort of an observatory.
Matthew
What about this one?
http://www.icas.to/space/Digital-camera ... igital.htm
At 500++ SGD, it ought to be the most expensive dustcover ever built.
Let me know if you have the facilities to prototype this glass. I am hoping Anat might be brewing something along this line too.
You are correct to say some H-alpha (such as Kenko, Lumicon) are long pass filters that extend to NIR. This LP can be work around if you stack an hot mirror which form a H-Alpha & SII bandpass, provided if you already have access to these combination. Otherwise 2” 45nm Ha may not be such a bad choice.
Admittedly, I have not considered the effect of SII “contamination” yet. More often than not, there are other mysterious factors that conspire to wreck my H-Alpha imaging attempts before SII does. These are just some issues we’ve got to live with without the comfort of an observatory.
Matthew