Telescope and Mount Suggestions

Here is the place to talk about all those equipment(Telescope, Mounts, Eyepieces, etc...) you have. Not sure which scope/eyepiece is best for you? Trash it out here!
thlightbrigade
 
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Telescope and Mount Suggestions

Postby thlightbrigade » Tue Sep 01, 2015 9:38 am

Hi everyone!

I'm new here and eager to begin this new hobby/passion in astronomy and, specifically, astrophotography.

I haven't set a budget because I really don't know where to begin but some information:
    - I want to view and take pictures of deep space primarily.
    - Not TOO bulky (I know they are all quite bulky tho lol. I have no car so... I need something that either I or my husband can carry around)
    - I'm thinking of something mid-range -- like not too beginner-ish but not that professional either... do I make sense? I want something that works well and is a good stepping stone to better equipment in the future but one that can last quite a while before I feel like "this doesn't allow me to do what I want to do already, I need a new telescope".
    - I have no equipment only a Sony DSC HX300 I use for random things (will this do?)

I know it's all over the place! Any suggestions or tips would be greatly appreciated. I've read up a little on types of telescopes and mounts but it's all still a little bit confusing because there's so much out there. Thought it would be great to hear from you folks who have had actual experience doing this either in Singapore or nearby places cause some things have to be taken into consideration like light pollution or whatnot I don't even know. Halp. Thanks!

Also if the camera I have won't work too well, please shout out and share your thoughts with me please! Thanks you guys!

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antares2063
 
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Re: Telescope and Mount Suggestions

Postby antares2063 » Tue Sep 01, 2015 2:44 pm

Hi and welcome to singastro, thlightbrigade.

Ill try to address your points but primarily Im a visual person, not into astrophotography (AP for short), so perhaps the others who are doing Imaging can help chip in or correct me.

"I want to view and take pictures of deep space primarily"

In a way no one scope can do both aspects of it perfectly. When you are talking about viewing and seeing objects at eyepiece , the limitation is our pupil size of the eyes. So from a visual standpoint, a bigger aperture enables one to see the faint and exotic stuff, be it nebulae, clusters, galaxies. Which is what some of us term as "faint fuzzies". But ALAS our Singapore light pollution is very severe, most of my fruitful use of my astro gear is in Malaysia dark sky sites.

Since you seem to be more inclined towards doing AP , start with a shorter focal length telescope , ideally a refractor <500mm. I think this is because a shorter FL scope is easier to get tracking/alignment of the EQ mount right. I.E the longer a scope one has when doing imaging, the more accurate and more zhun it must be to prevent stars from bloating or trailing.

-- Not TOO bulky (I know they are all quite bulky tho lol. I have no car so... I need something that either I or my husband can carry around).

From imaging Point again, get a mount that is able to tahan the weight of your final imaging train. So not just the one telescope, but including the main scope's tuberings, your camera , the guidescope, and the guidecam attached to the guidescope. The wires leading to the mount and laptop. Therefore the mount must be more than adequate to hold all this with ease.

As for third point , I think maybe its better for the imaging pple to advise, also need to bear in mind a lot of factors.

I have no equipment only a Sony DSC HX300 I use for random things

Not sure how long your camera can expose for one frame. But most of the imaging buddies I know uses Canon or Nikon DSLR. After alignment and checking that the tracking is perfect, can expose up to 3mins or beyond, once again taking into account other factors to consider. All of their nice images of nebulas are a end result of taking many frames of the same object. For example, 20 frames of 3mins each, equalling a total time of 60mins.
Also there are various types of astronomy-usage only cameras. Examples include One-shot Colour, Monochrome and Narrrowband using appropiate filters such as H-alpha, Sulphur 2 and Oxygen 3.

Hope I have helped answer some of your queries, do try to join in local sessions to look at various setups before committing your $$$ :)

Regards
Junwei
I miss the place where stars shine bright, to gaze upwards in awe of the sight

thlightbrigade
 
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Re: Telescope and Mount Suggestions

Postby thlightbrigade » Mon Sep 07, 2015 10:40 am

Oh my gosh, I love your extensive response. Thanks so much for taking the time.

a bigger aperture enables one to see the faint and exotic stuff


So how big? f/12? f/6? Is 6 enough?
Also the shorter the focal length the better? 120mm is ok?

For example, 20 frames of 3mins each, equalling a total time of 60mins.


You mean they do the 3min exposure thing 20 times and then use some photo editing software to combine all 20 pics? Wao. So if my camera can do 3mins then it's good enough you think?

Also there are various types of astronomy-usage only cameras. Examples include One-shot Colour, Monochrome and Narrrowband using appropiate filters such as H-alpha, Sulphur 2 and Oxygen 3.


Do not understand this at all. When you say filters, are they physical filters or computer editing filters? I am assuming those filters help bring out the colour in the B&W pics taken with the astronomy-usage only cameras...?

do try to join in local sessions


I WOULD LOVE TO, it seems like it doesn't happen very often tho? Do you go all the time? I want to drop by say hi and ask many questions and yes, look at various setups (my gosh there's so much to learn).

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ivan
 
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Re: Telescope and Mount Suggestions

Postby ivan » Mon Sep 07, 2015 6:58 pm

Hi, to answer some of your questions:
1. Aperture in this case does not refer to the focal speed (i.e. f-ratio). It refers to the size of the objective lens or primary mirror (e.g. 4 inches, 6 inches etc)
2. The process of combining individual short exposures is called stacking, and yes it simply means the camera would just need to do 3 minutes of exposure, 20 times over. However, it is not usually the camera that sets the fundamental limit for exposures, but rather the ability of the mount to track accurately for the duration of that 3-minute exposure.
3. Filters are physical filters. These are made to pass specific wavelengths of light emitted only by objects in space. However, no need to fuss about these at the moment.

Additionally, from the point of view of deep sky astrophotography, the first consideration for the investment you make should go into getting a motorised equatorial mount. The scope used then follows secondarily. Unlike visual astronomy, one does not need a large telescope to capture good images of deep sky imagery. In this case, we are more concerned with the focal speed of the scope (f-ratio; the faster the better), and optical performance in delivering sharp and aberration-free stars. In general, a small apochromatic refractor is usually recommended for this purpose. Regarding the mount, this is where most of the weight (and cost) will come in; an equatorial mount involves motorised tracking units, metal components for the gear drive, as well as counterweights. Once again, before committing to a purchase, do go down to local sessions to speak to the people there to gain a better sense of what equipment is suitable for your purposes.

As for cameras, DSLRs (regardless of brand, make, model) are usually a starting point for astrophotography as it enables what is known as prime focus imaging. Using suitable adapters, the telescope is essentially transformed into a long focal length telephoto lens, which is then used to capture the stars. DSLRs can be modified to remove the IR filter to allow certain types of nebulae to be better seen. If you intend to modify your DSLR, I would suggest buying one off the secondhand market on clubsnap (which can fetch for as low as $150) and then modifying it.

Hope this helps.

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antares2063
 
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Re: Telescope and Mount Suggestions

Postby antares2063 » Mon Sep 07, 2015 7:09 pm

Thanks Ivan for replying too (thumbs up)

Yes local sessions dont happen that often, theres one active group in Bishan and one in Ang mo Kio. For myself i sometimes will post here when i intend to observe ..but the haze pretty much kills everything now.

Regards,
junwei
I miss the place where stars shine bright, to gaze upwards in awe of the sight

thlightbrigade
 
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Re: Telescope and Mount Suggestions

Postby thlightbrigade » Thu Sep 10, 2015 3:56 pm

Hi guys

Thanks so much for the responses. I'll go read up more and wait for the haze to die down and hope there'll be some sessions soon where I can join, meet you guys and learn more about this.

So my steps now are...
1. Look at motorised equatorial mounts. (question tho, when I buy a mount, will it come with the counterweights and metal components for the gear drive that ivan mentioned?)
2. Get a DSLR (ivan said modifying it... but how? Get new lenses? I know photographers are all about the lenses haha. Or like change parts inside the camera?)

Any sessions in the west hahaha. Junwei, when you go and stargaze, do you stay around your area for that or is AMK and Bishan better so you go there or what eh?

Thank you again!

Dark Neptune
 
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Re: Telescope and Mount Suggestions

Postby Dark Neptune » Thu Sep 10, 2015 6:40 pm

Hello,

I live in the west but don't really do stargazing sessions on my own nowadays. Have you tried going down to the Science Centre Observatory? I'll be there next friday with my own scope, with my other friends. :)

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antares2063
 
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Re: Telescope and Mount Suggestions

Postby antares2063 » Fri Sep 11, 2015 4:31 pm

Modifying dslr makes it unsuitable for normal use anymore, it involves removing a built in compoment , nothing to do with the lens but the mod has something to do with the sensor. I cant explain it very well, but u can google search "modified dslr + astrophotography"

I stay in the east so i dont really travel there. Mostly i stargaze at ...Mersing haha. Locally its at Haig girls school field (currently status unknown or Lorong ong lye field or east coast park. But dont expect much as the Light pollution of sg is everywhere.

Regards
Junwei
I miss the place where stars shine bright, to gaze upwards in awe of the sight

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ivan
 
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Re: Telescope and Mount Suggestions

Postby ivan » Sun Sep 13, 2015 10:47 am

Most EQ mounts are sold as a package. Normally it is the higher end ones that require you to purchase additional components separately. One important thing to note is to make sure that the counterweights provided are suitable for your OTA weight.

As Junwei mentioned, DSLR modification involves removing the in-built IR filter. The effect of this is to increase the sensitivity of the DSLR sensor to certain types of nebulae. However, you can still take pictures using an unmodified DSLR.

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cloud_cover
 
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Re: Telescope and Mount Suggestions

Postby cloud_cover » Mon Sep 14, 2015 3:54 pm

Hello!
Visual and Astrophotography are really 2 separate branches of astronomy - Visual requires large aperture. The bigger the aperture, the better you see. Focal ratio is not important as it only determines the magnificantion and field of view. Photography however requires fast focal ratios. Imaging times increase by a factor of 2 for each increase in f stop. For example, from f4 (most imaging newtonians) to f8 (most apochromats not specifically designed for imaging), that's 2 f- stops. You'll therefore need 4x the exposure time to achieve the same result. Aperture is not important - aperture only determines the field of view of your image because focal length = aperture multiplied by f number.
Having said all of that, nothing, absolutely nothing can beat dark skies. A larger aperture is nice (I have a 14" - I think there's a 24" lurking around) but nothing will beat driving an hour or so up north for significantly darker skies, both for visual as well as for AP.

With regards to modifying a DSLR, the reason is that all DSLRs not specifically designed for AP (these are the Canon 60Da and the Nikon D810a) have a low pass filter that blocks red light specifically in the Hydrogen-Alpha wavelength, which is the most important wavelength in astronomy because the universe is mostly made up of Hydrogen (and ignorance, quote from Weixing :) ) An unmodified DSLR has a 5-10x less sensitivity to this wavelength. What it means is that when taking images of emission nebulae (such as Orion, Lagoon, Swan, Eagle etc nebulas), it will be 5-10x less sensitive. However, it will work just as well for galaxies, star clusters, reflection nebulae. Using a modified DSLR, which has this low pass filter removed, for regular photography will result in pictures having a reddish cast. This can be easily fixed by using a custom white balance or shooting in RAW and adjusting the pictures later. Some modifications may cause the autofocus mechanism to fail due to the refractive properties of the low pass filter itself. If you want to venture into modified DSLRs, I highly recommend you buy a used item. You can get them occasionally here or on resale sites such as http://www.clougynights.com classifieds or http://www.astromart.com Generally if you strike a reasonable deal you can re-sell it again without too much loss.
However, let me emphasize something about modified DSLRs:
1. You don't NEED one to start astrophotography
2. You CAN still take nice shots of emission nebulae, especially the brighter ones.

For motorized equatorial mounts - not just any one will do and don't always believe the advertising. If you want a reasonably pleasant experience, you'll need one of reasonable quality. Look up the reviews for your specific mount and unless you're buying a high end mount, divide the weight limit by 2 or 3 for an astrophotographical load. Also make sure its able to reach down to 0 deg because we live on the equator. A large number of mounts, especially the older models are unable to to do this without a special wedge. If you exceed 400-500mm of focal length, you'll generally want guiding, which means either a stand-alone device or a laptop and CCD.

I hope I haven't discouraged you! Personally I think one of the best ways to start Astrophotography is to do wide field. You can, without tracking, go up to 30 secs with a 50mm lens or more with a wider lens. If you choose a clear night, even with the light pollution in Singapore you can still get a pretty star field. I did this one a few years ago in Singapore of the Scorpio and M7 cluster without filters, others have done much better:
Image

I also got this one with a 70mm camera lens, a Skywatcher Star Adventurer (one of those portable EQ mount heads meant for cameras) in a dark sky on holiday
Image

Hope this helps!
DON'T PANIC

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