Thanks.
That means the DSI can't take wide field....
Anyone knows how to change or shorten the Starblast focuser?
Its up to you to decide. Do you want wide or resolution?
Of course, if u want both, then u need extreme equipment. Equipment with long enough focal length to give u the resolution and enough megapixels to give u the wide field. Then the scope will need a huge corrected flat minimally vignetting view. Well, if some schools build their observatories with foresight, then we would have such a setup in Singapore.
Meng Lee
Of course, if u want both, then u need extreme equipment. Equipment with long enough focal length to give u the resolution and enough megapixels to give u the wide field. Then the scope will need a huge corrected flat minimally vignetting view. Well, if some schools build their observatories with foresight, then we would have such a setup in Singapore.
Meng Lee
Photo Album:
http://www.flickr.com/photos/14113965@N03/
http://www.flickr.com/photos/14113965@N03/
"The universe is composed mainly of hydrogen and ignorance." -
orly_andico
- Posts: 1616
- Joined: Sun Aug 09, 2009 11:14 pm
- Location: Braddell Heights
- Contact:
one idea I had this morning on the subway....
Sony NEX-3 or NEX-5
or Panasonic GF1 and friends.
since these are mirrorless designs, they require much less back-focus than an SLR.
and in the case of the GF1 and other micro-43 the sensor is 1/2 the area of the APS-C sensor, so less problems with off-axis vignetting and coma.
(the Sony has an APS-C sensor though)
but the cost is an issue... you can get a decent 80mm APO for the price of one of these cameras (and use that for imaging). i think a Megrez 72 or ZS80 with a flattener would still come in under $1.2k SGD (cost of an NEX-3) and would be a better imaging scope than an obstructed one...
Sony NEX-3 or NEX-5
or Panasonic GF1 and friends.
since these are mirrorless designs, they require much less back-focus than an SLR.
and in the case of the GF1 and other micro-43 the sensor is 1/2 the area of the APS-C sensor, so less problems with off-axis vignetting and coma.
(the Sony has an APS-C sensor though)
but the cost is an issue... you can get a decent 80mm APO for the price of one of these cameras (and use that for imaging). i think a Megrez 72 or ZS80 with a flattener would still come in under $1.2k SGD (cost of an NEX-3) and would be a better imaging scope than an obstructed one...
A dedicated astro CCD is a big leap over a typical DSLR for the following reasons
It's cooled and has far lesser noise
It's 16bit compared to 12bit or 14bit on DSLR, which means far better dynamic range
It's mono, no bayer matrix here
Higher QE
It outputs real RAW, not some cheesy camera enhanced "raw"
Pixel size is just right, not puny like current DSLR, this means more sensitivity and dynamic range
It's more sensitive, doh
If you can afford it, higher class sensors have lesser "defective" pixels
No H-Alpha robbing IR-Cut filter
No shaking from mirror box
Really long exposure, not some wierd bulb mode
No worries about running out of battery during an exposure, this thing runs on your laptop.
It's T-Thread and works with far more accessories
As menglee has mentioned, resolution is determined by pixel size and focal length and is measured by arcsecond/pixel. Having megapixel cameras just mean you capture more empty patches of sky and end up cropping more.
Widefield or not is not solely dependable on the size of the chip, but also a function of the focal length of the lens. The sensor inside your iPhone is prolly far smaller than the smallest astro CCD, but has a much wider FOV.
Most people assume that you need a high megapixel camera to deliver really sharp prints. Not very true. Megazine quality prints are done at 300 pixels per inch. When i say megazine quality, I mean National Geographic.
For most prints, you should be able to get away with just 150-200 pixels per inch. Anything less than 100 pixels per inch doesn't look that sharp anymore. For a 800x600 camera, one should be able to get away with 4r kind of prints. Moving on to slightly better ccd at 1600x1200, one should be able to get decent 8r prints.
~MooEy~
It's cooled and has far lesser noise
It's 16bit compared to 12bit or 14bit on DSLR, which means far better dynamic range
It's mono, no bayer matrix here
Higher QE
It outputs real RAW, not some cheesy camera enhanced "raw"
Pixel size is just right, not puny like current DSLR, this means more sensitivity and dynamic range
It's more sensitive, doh
If you can afford it, higher class sensors have lesser "defective" pixels
No H-Alpha robbing IR-Cut filter
No shaking from mirror box
Really long exposure, not some wierd bulb mode
No worries about running out of battery during an exposure, this thing runs on your laptop.
It's T-Thread and works with far more accessories
As menglee has mentioned, resolution is determined by pixel size and focal length and is measured by arcsecond/pixel. Having megapixel cameras just mean you capture more empty patches of sky and end up cropping more.
Widefield or not is not solely dependable on the size of the chip, but also a function of the focal length of the lens. The sensor inside your iPhone is prolly far smaller than the smallest astro CCD, but has a much wider FOV.
Most people assume that you need a high megapixel camera to deliver really sharp prints. Not very true. Megazine quality prints are done at 300 pixels per inch. When i say megazine quality, I mean National Geographic.
For most prints, you should be able to get away with just 150-200 pixels per inch. Anything less than 100 pixels per inch doesn't look that sharp anymore. For a 800x600 camera, one should be able to get away with 4r kind of prints. Moving on to slightly better ccd at 1600x1200, one should be able to get decent 8r prints.
~MooEy~
-
timatworksg
- Posts: 767
- Joined: Mon Feb 01, 2010 9:42 pm
- Location: Pasir Ris
![[smilie=warning.gif]](./images/smilies/warning.gif "warning")
....lolI get the point about a dedicated astro CCD and agree that DSLRs are plagued by a variety of problems. CCDs it is obviously much more effective and efficient.
But the main drawback is the laptop.
I ain't doing my imaging at home or anywhere near a power plug (power supply = lights), it is just too bright. Thus, the set-up will have to be mobile.
The powertank battery can last a night, but the laptop batteries on average can only last 2 hours.
Anyone have any ideas on how to overcome this problem? If so, I am getting a CCD to cut all the crap with DSLRs.
@Minglee: It seems like Mr Kwan is setting up an observatory for AGastro.... So, the better set-up will be in the near future.
But the main drawback is the laptop.
I ain't doing my imaging at home or anywhere near a power plug (power supply = lights), it is just too bright. Thus, the set-up will have to be mobile.
The powertank battery can last a night, but the laptop batteries on average can only last 2 hours.
Anyone have any ideas on how to overcome this problem? If so, I am getting a CCD to cut all the crap with DSLRs.
@Minglee: It seems like Mr Kwan is setting up an observatory for AGastro.... So, the better set-up will be in the near future.
Hey,
I like the phrase "cheesy raw".
Indeed netbooks work well and last long enough. (But I don't think I recommend netbooks for planetary photography.)
Well there are 2 ways:
1) Big batteries. Try to calculate the total current drawn by the goto mount and the ccd camera so as to determine if the power tank is enough for that.
2) Long extension wires. As you can see, Remus and I are adopting this method to reduce possible problems due to dead batteries. Well, his problem is much bigger, the total consumption of his mount (2A), camera (2A) and mac (few A) is enough drop the idea of big batteries.
I don't know about the setup for AGastro so I can't say if it is imaging ready.
I like the phrase "cheesy raw".
Indeed netbooks work well and last long enough. (But I don't think I recommend netbooks for planetary photography.)
Well there are 2 ways:
1) Big batteries. Try to calculate the total current drawn by the goto mount and the ccd camera so as to determine if the power tank is enough for that.
2) Long extension wires. As you can see, Remus and I are adopting this method to reduce possible problems due to dead batteries. Well, his problem is much bigger, the total consumption of his mount (2A), camera (2A) and mac (few A) is enough drop the idea of big batteries.
I don't know about the setup for AGastro so I can't say if it is imaging ready.
Photo Album:
http://www.flickr.com/photos/14113965@N03/
http://www.flickr.com/photos/14113965@N03/