17 replies to this topic

[GraySkies]

I'm looking at getting hyperstar for my 8" EdgeHD this year as my "astronomy purchase" and I'm wondering if it will work better if I attach my Sony A7s (Full Frame 10MP large Pixel Pitch) or my GH4 (MFT 16MP small Pixel Pitch) in terms of which will likely produce better results (So I can purchase the right camera adapter). I'm wondering if anyone has any experiance with either combination, eventually I'll go CCD but for now I'm trying to avoid a computer in the field but know I'll eventually have to go that route if I want to improve.

[mmalik]

Although a7S has larger pixels, I would give it a try first. I doubt you'll go the CCD route if you used a7S to its capabilities. Regards

[t_image]

Grayskies,

Your "better results" is a very vague requirement and betrays you may not understand the complexities and variables involved with AP.

The two cameras are different tools and have different benefits given different settings......

It would be better if you either specified more details concerning your workflow and objectives, or ideally

purchased adapters for both since they are inexpensive compared with the investment you have already made in the hobby,

and use them for what they are good at......

 

As to your question about the difference in sensor and pixel size,

everything else being equal, the ideal is to have the best resolution match for the focal length and target and seeing conditions you have......

Play around with this site (make sure in imaging tab)

it has both cameras and can simulate the different FOV of targets and will give you resolution values with different telescopes.....

It will also take into account any focal reducers or barlows you add to the train......

http://astronomy.too.../field_of_view/

 

There is a lot already posted on CN concerning the pros and cons of the a7s, I recommend you do a few searches for such as one link won't give you the whole "picture"....

Search for "bit depth" and "star eater" to start with......

There are a few on here I've seen using the GH4, less though......

Both will give you a good live view so you can focus a target......

The a7s wins out in low noise and higher ISOs for quicker subs.......<but that's a certain style of workflow that not everyone uses.

Many a7s benefits are best seen with fast lenses and hyperstar setups with focal ratios of f/2.8 and faster...

Going higher mag and darker f/ ratio makes more things equal except for such mentioned above....

Cheers!

[GraySkies]

T_image

My concerns with both cameras is over/under sampling, Hyperstar should be able to cover the A7s Full Frame however I'm concerned at only 10MP that I'll get under sampling issues. The GH4 is half the FOV and 16MP so the opposite problem exists, oversampling.

I'll see about getting both adapters and checking out what works best for my sky conditions, but I was hoping people have tried this and could provide input/example images to give me an idea of what to expect.

[bobzeq25]

I'm looking at getting hyperstar for my 8" EdgeHD this year as my "astronomy purchase" and I'm wondering if it will work better if I attach my Sony A7s (Full Frame 10MP large Pixel Pitch) or my GH4 (MFT 16MP small Pixel Pitch) in terms of which will likely produce better results (So I can purchase the right camera adapter). I'm wondering if anyone has any experiance with either combination, eventually I'll go CCD but for now I'm trying to avoid a computer in the field but know I'll eventually have to go that route if I want to improve.

Tough call, either could work. 

 

People disagree about whether undersampling or oversampling is better.   Undersampling gives better signal to noise ratio, and is recommended by at least one expert I know, Charles Bracken.  Oversampling gives better stars, and, if your tracking and seeing is up to it, better resolution. 

 

This is one of many cases in AP where all depends on you, and the best idea is to try them both, see what works for you.

Edited by bobzeq25, 01 August 2016 - 02:40 PM.

[Alien Observatory]

Maybe a little bad news.  The 8" Edge / Non Edge Hyperstar does not have the back focus to accommodate a DSLR.  Good Luck and please let us know if you get it to work....Alien Observatory

[GraySkies]

A.O. That's why I'm proposing Mirrorless cameras, they have similar back focus to Astro CCDs.

[Alien Observatory]

I did try my Nikon5500 and it almost came into focus, I believe 25mm back focus is about the maximum the Hyperstar (8") based on my experience.  Keeping in mind that some type of C mount adapter will be needed for the cam.

 

I was able to trade the 8" edge tube (with Hyperstar) for an almost new non edge CPC 9.25 so that I may use any standard DSLR.  Here is a link to some back focus distances.  Good Luck with your project.  Patrick

 

https://en.wikipedia..._focal_distance

[Ladyhawke]

I'm looking at getting hyperstar for my 8" EdgeHD this year as my "astronomy purchase" and I'm wondering if it will work better if I attach my Sony A7s (Full Frame 10MP large Pixel Pitch) or my GH4 (MFT 16MP small Pixel Pitch) in terms of which will likely produce better results (So I can purchase the right camera adapter). I'm wondering if anyone has any experiance with either combination, eventually I'll go CCD but for now I'm trying to avoid a computer in the field but know I'll eventually have to go that route if I want to improve.

 

Neither will work. Only SCTs 9.25 and up can be used with DSLRs. They obstruct too much and cannot be used with an 8", for the Edge 800 you need a cylindrical CCD or CMOS camera. It has nothing to do with focus, it's just too much obstruction for an 8".

[t_image]

Obstruction is a good point..

Here's a different mirrorless camera with an 8" and hyperstar:

http://www.cloudynig...ager/?p=7042302

[Alien Observatory]

That QX1 looks interesting...

[GraySkies]

Ah the obstruction... Yes that would put a damper on my plans... I thought I could get away with a small camera but if the census is No, I'll need to purchase a Cylinderical CCD...

[dkeller_nc]

If your concern about a computer in the field is about bulk/weight, then you might want to consider a Surface tablet.  The Surface 4 runs a full version of Windoze 10, and (if purchased that way) has more than sufficient RAM to run just about any capture/processing software you could choose. And it's easy to "harden" a Surface tablet compared to a laptop with an appropriate case, so it'll be relatively sturdy.   Pair it with ZWO's ASI1600 cooled color camera, and you've a very compact package that's relatively inexpensive as well.

[GraySkies]

I'm moving towards a permanent observatory, so computer/weight etc will soon be a thing of the past. However I'm having to do this on a shoe string budget so additional costs like a new camera is pushing my limits at the moment, if it's required for Hyperstar I may have to forgo the Hyperstar upgrade this year :/

[Michael Miles]

I'd say give it a try.  Maybe Starizona will cut you a deal if you're buying 2 adapters by only getting one Hyperstar piece and 2 back pieces (the piece that attaches to the Hyperstar is the same in all their adapters).  I use my Canon EOS-M and M3 mirrorless cameras with my Hyperstar:

 

http://www.cloudynig...kenscope/page-5

 

This post is for the adapters I made myself. but I ended up buying a starizona adapter since I didn't want to go through the hassle of making one that would hold a filter.  They custom built my adapter (which now anyone can order since it was done as a CAD/CAM design).  The EOS-M and M3 both have an 18mm flange-to-focal-plane distance like the mirrorless Sony's.  However, the Canon has a smaller body, and ends up giving a nice 4 spike diffraction pattern (I'm an old Newtonian guy) which can be moderated by using an eliptical mask as presented elsewhere on this forum.

 

Go for it and good luck,

 

Michael 

[Michael Miles]

I finally got my Hyperstar C8 setup out this past weekend (between Olympics viewings .  I recently purchased a used C8 with the Fastar secondary.  The thing I wanted to mention is that I'm using a Canon EOS-M# which has the APS-C sized sensor, and I'm getting vignetting.  The implication is that the full-frame camera would have even worse vignetting.  I think the C8 Hyperstar is designed for approximately an APS-C CCD size.

 

Michael

[Michael Miles]

Whoops - that's a Canon EOS-M3 (timed out on the edit post option).

[rockstarbill]

I'm moving towards a permanent observatory, so computer/weight etc will soon be a thing of the past. However I'm having to do this on a shoe string budget so additional costs like a new camera is pushing my limits at the moment, if it's required for Hyperstar I may have to forgo the Hyperstar upgrade this year :/

 

Just sent you a PM, since I am selling my Hyperstar lens and a cylindrical camera that works incredibly well with it (QHY8L).