Astrophotography Setup

[Danny Crosgrey]

Hello,

This is my first post on the site.   Nice to see so much helpful information.

I have been interested in beginning astrophotography for some time.  I am looking to be able to take images of large DSOs such as the Andromeda Galaxy.  Recently, I have been looking at the equipment I would like to get for this setup.  I am planning to use a William Optics Zenithstar scope on a Skywatcher HEQ5 Pro mount.  I will be using the field flattener for the Zenithstar and the camera I will be using is the Canon 3Ti (astro modified).  

My question is:  Given that I want to ensure that the field of view is large enough to image galaxies such as M31, should I go with the Zenithstar 61 APO or the Zenithstar 73 APO.  Would the Zenithstar 73 allow the Andromeda Galaxy to fit within the frame given this setup?  Was thinking that the extra aperture would give better views visually during the odd times that I would want to do visual observing of planets, etc but don't want to limit the objects I can fully image.

 

Thanks in advance for any insight you can provide. 

Dan. 

[Guest]

Hello

Danny Crosgrey

Welcome to SGL,

You can calculate the FOV here..

https://astronomy.tools/calculators/field_of_view/

 

I did not find your canon, took the next best.. 600d and with the setup you have, the Andromeda would loook his way.

Regards

Martin

 

[Guest]

Below you will find both 61 and 73 scopes.

 

 

 

[dannybgoode]

M31 needs a particularly wide FoV and I would be cautious tailoring an AP set up around a single target. 

I too really want M31 in the bag and I could do it with a bit of faffing around but have compromised elsewhere in my setup for future purposes. 

Also , if you haven’t already get hold of a copy of Making Every Photon Count. I know everyone recommends it but with good reason. I’m on my third read through and there is just so much more to AP than I ever imagined. 

Good luck and don’t get too addicted  

[Adam J]

1 hour ago, Danny Crosgrey said:

Hello,

This is my first post on the site.   Nice to see so much helpful information.

I have been interested in beginning astrophotography for some time.  I am looking to be able to take images of large DSOs such as the Andromeda Galaxy.  Recently, I have been looking at the equipment I would like to get for this setup.  I am planning to use a William Optics Zenithstar scope on a Skywatcher HEQ5 Pro mount.  I will be using the field flattener for the Zenithstar and the camera I will be using is the Canon 3Ti (astro modified).  

My question is:  Given that I want to ensure that the field of view is large enough to image galaxies such as M31, should I go with the Zenithstar 61 APO or the Zenithstar 73 APO.  Would the Zenithstar 73 allow the Andromeda Galaxy to fit within the frame given this setup?  Was thinking that the extra aperture would give better views visually during the odd times that I would want to do visual observing of planets, etc but don't want to limit the objects I can fully image.

 

Thanks in advance for any insight you can provide. 

Dan. 

I think that you need to abandon this idea about needing to fit M31 into the frame as sooner or later if you progress in the hobby you will most likely end up buying a dedicated camera, most likely mono and that means that the sensor will be smaller unless you are willing to spend allot of money and you will have to do multiple pains to cover m31 anyhow.

Personally I think that the Z73 is better for you in the long term than the z61 and I would even suggest going for a 80mm instrument if it was me.

I would not try and visually observe with the same scope that I image both the Z73 and Z61 are inadequate for this especially for planets. 

Adam

[Danny Crosgrey]

Thanks to everyone for your replies.  You all make some good points.

Another question - I will likely be purchasing my reflector in the next few months along with the guide scope.  I was looking at William Optics because I have heard from many people that they are good quality and the price seems reasonable too.  My question is, would you recommend that I look at either their Zenithstar 126mm or 103mm options if I can swing it?  Does aperture make a difference for astrophotography?

Just curious as to what the benefits are and what I should be considering when investing in this scope?  I will be sticking with this equipment for some time so want to ensure I am making the right choice.

 

Thanks again for your help and insight.

Dan.

[Danny Crosgrey]

Forgot to mention that I will be using the Canon T7i as my astroimaging camera (it has been astro modified).

[Adam J]

17 hours ago, Danny Crosgrey said:

Thanks to everyone for your replies.  You all make some good points.

Another question - I will likely be purchasing my reflector in the next few months along with the guide scope.  I was looking at William Optics because I have heard from many people that they are good quality and the price seems reasonable too.  My question is, would you recommend that I look at either their Zenithstar 126mm or 103mm options if I can swing it?  Does aperture make a difference for astrophotography?

Just curious as to what the benefits are and what I should be considering when investing in this scope?  I will be sticking with this equipment for some time so want to ensure I am making the right choice.

 

Thanks again for your help and insight.

Dan.

More aperture and hence focal length will provide more detailed images for any given pixel size camera.

In terms of data collection speed then F-ratio and pixel scale are the factors you need to consider.

At constant pixel scale a larger aperture will generate a given signal to noise ratio faster.

At constant F-ratio any given camera will generate given signal to noise ratio at the same speed irrespective of aperture.

So in essence unless you bin your pixels to achieve the same pixel scale with a larger aperture as you did with a smaller aperture scope of the same f-ratio you will not notice much difference in the time it takes you to get to the same signal to noise ratio irrespective of aperture.

As such in most situations aperture will not matter as much as F-ratio when imaging but there are exceptions.

For example for galaxies the optimal arc-seconds / pixel to resolve maximum detail is lower than for most emission nebula and hence you will want a longer focal length and might be willing to accept a slightly lower f-ratio. However you can also achieve this to a degree by selecting a camera with smaller pixels.

In the end if I wanted a scope for visual and imaging that was not so long a focal length as to provide too narrow a FOV / make guiding too hard for a beginner / not require a expensive mount while also providing a useful amount of aperture for visual then I would be getting a 102mm class F7 FPL53/ FCD100 triplet or doublet depending on budget.

Adam

 

 

 

 

 

[ollypenrice]

The simple rules governing F ratio's effect on exposure time with camera lenses do not necessarily apply in astrophotography but this debate is probably beyond what's needed here.

Many DSOs are large, M31 (if imaged in depth) is far larger than it appears in the very helpful simulations posted by Artem and would not fit on the chips as shown. If you were to go for a slightly longer focal length by going for more aperture (100 to 130mm or so) the biggest change you'd notice would be a reduced field of view. You would, if the guiding and seeing allowed it, resolve slightly more detail but you might not actually manage to do so. In this case your reduced FOV would be without benefit and you'd be making life harder for yourself by asking a lot more of the mount in terms of payload and tracking accuracy. As a first scope and a keeper I'd go for something of 80mm aperture or less and learn the craft on relatively widefield projects which will be more tolerant of imperfections in the system.

I use only two focal lengths, 530mm and 1015mm, With these I can tackle pretty much any target in the sky so far as long exposure DS imaging goes, provided I match pixel size to scope. The long FL system is less productive because, as well as needing a clear night, we need a night of good seeing or we won't be exploiting the high resolution of the system.  That's why I'd advise you to keep to a short focal length for starters and worry about small galaxies and planetary nebulae a few years down the line.

Basically it's hard enough as it is so any simplification is to be embraced!

Olly

 

[Danny Crosgrey]

Thanks for the feedback.  What would be your thoughts between the Zenithstar 73mm and 61mm scopes? Would I have an easier time with one compared to the other or would it be about the same?  I was originally thinking of the 73 but would appreciate everyone's thoughts.  I will be using a Canon T7i for image capture. 

 

Dan. 

[Danny Crosgrey]

Another add-on question..... Would there be a benefit to getting the William Optics Star 71 vs the Zenithstar 73?  I read that the WO Star had a 5 element design. I know that the Zenithstar 73 is a doublet.  Just wondering what differences or improvements I could expect. 

Thanks for all your help and support. 

Dan. 

[Owmuchonomy]

In your shoes I would delay getting a scope and use a lens on your camera attached to your HEQ5. This is exactly what I did for my first DSO (M31). I used a Canon 300mm f/4 lens purchased used from an auction site. I sold it back for the same price a few months later. I then looked at imaging scopes and ended up with an AA 102 triplet for DSOs but that’s another story.

[Adam J]

6 hours ago, Danny Crosgrey said:

Another add-on question..... Would there be a benefit to getting the William Optics Star 71 vs the Zenithstar 73?  I read that the WO Star had a 5 element design. I know that the Zenithstar 73 is a doublet.  Just wondering what differences or improvements I could expect. 

Thanks for all your help and support. 

Dan. 

The only reason to go with something bigger than the 73mm / 80mm scope when starting out is if as you said above, you also want to do some visual work.

If it was me and I wanted something for visual and AP then I would go with the 102mm

If not then the Z73 will work well for you.

From what I have heard the star 71 is a great scope if you get a good one and a royal pain if you dont....

Color correction on the 73mm fpl53 / lanthanum doublet will be pretty good and the simple doublet design and F6 is less likely to give you problems when starting out. 

Don't forget to get the the flattner.

Adam

[Danny Crosgrey]

Thanks for the reply, Adam.  

I have heard good things about the Explore Scientific ED102CF.  I am thinking that scope with a focal reducer/flattener may give me the best of both worlds.  It is also a triplet which will add to the image quality.  Would you see any challenges with this option as a refractor for someone starting out?  I plan to stick with the scope for a long time and learn as much as I can with the setup.

Has anyone had any experience with this scope?  I would likely go with an EQ6R Pro mount rather than the HEQ5 Pro because of the larger scope size.

 

Thanks again for your feedback.

Dan.

[ollypenrice]

A focal length of 714mm might land you in a something of a no man's land. It's a bit long for the larger nebulae and yet too short for most of the small galaxies. I used to think this about FLs of a metre but as pixels have become smaller the implications of focal length have evolved. 

Personally I'd go for a small refractor on GEM mount for imaging and an inexensive 8 inch Dob for visual rather than try to compromise between conflicting requirements. There wouldn't be much difference in cost.

Olly

[Adam J]

On 13/03/2019 at 07:52, ollypenrice said:

A focal length of 714mm might land you in a something of a no man's land. It's a bit long for the larger nebulae and yet too short for most of the small galaxies. I used to think this about FLs of a metre but as pixels have become smaller the implications of focal length have evolved. 

Personally I'd go for a small refractor on GEM mount for imaging and an inexensive 8 inch Dob for visual rather than try to compromise between conflicting requirements. There wouldn't be much difference in cost.

Olly

Surly you would use a 0.8 reducer with that though for 550mm.

[ollypenrice]

3 hours ago, Adam J said:

Surly you would use a 0.8 reducer with that though for 550mm.

Fair point and 550mm is a productive FL.

Olly