8 replies to this topic

[Cytoxan]

I’m looking for a proper guide scope for use on my 11” EdgeHD with HyperStar. I already have the asi120MM, but don’t think my AginaAstro 30mm freebie scope will work. Any recommendations?

[Ljubo]

Well, I do have an William Optics 32mm guide scope guiding RASA 11'' , and it guides well. So why don't give your 30mm guide scope a try?

[Cytoxan]

I probably will use it, just wanted to know if it's appropriate. It's only 120mm, and 200 to 400 is recommend.

[cuzimthedad]

Moving to Beginning Deep Sky Imaging...

[Andros246]

A 120mm mini and 30mm guide scope is perfectly capable of guiding at .6-.8” reliably mount dependent of course.
 

which is considered excellent guiding for a setup with a arc second per pixel of around 1.44” which yours is.

 

The “recommendations” are far outdated we have multi star guiding and improved sub pixel resolution accuracy inside PHD2 now.

 

However if possible with the hyper star  if you want to “min max” you can go off axis guider which would also take flexure out of the picture.

Edited by Andros246, 22 January 2025 - 10:30 PM.

[Drothgeb]

I’m looking for a proper guide scope for use on my 11” EdgeHD with HyperStar. I already have the asi120MM, but don’t think my AginaAstro 30mm freebie scope will work. Any recommendations?

That combo is perfectly fine to guide the Hyperstar with.

[Patrick]

I probably will use it, just wanted to know if it's appropriate. It's only 120mm, and 200 to 400 is recommend.

 

I'm not sure what your main imaging camera is, but you should be well within the1:5 "imaging scope to guide scope ratio" rule of thumb.  You can calculate the actual value using astronomy.tools calculator "Guidescope Suitability" .

 

Patrick

[BucketDave]

Your 11 inch hyperstar (so assuming F2.0) ought have a focal length around 550mm. So if you use the old rule (3:1 to 5:1), that suggests a guide scope focal length in the 100-200mm range. And that's where mini guide scopes sit. I think your 200-400mm recommendation is wrong.

My mini-guide scope (FL=126mm) guides around 1.0 to 1.5" RMS but i find it very difficult to achieve decent focus. Its objective screws in/out and has a lock ring - tightening the lock ring changes focus. If i were to buy another, I'd have a fixed objective and a helical focusser at the back.

Edited by BucketDave, 23 January 2025 - 05:28 AM.

[Drothgeb]

My FMA135s (137mm fl) regularly guide at 0.3” - 0.5” RMS with my CEM70 depending on the seeing. On nights with excellent seeing, I’ve seen extended periods below 0.3”. But, they are a good bit sharper than the typical 30mm guide scope, and have a great focuser. I use them up to 1080mm fl, and always get round, tight stars. 

 

I’ve used them on scopes that I also have a OAG, I get the same results either way. Both will guide to the limits of the mount.
 

It’s better to use a small, sharp guide scope that doesn’t contribute to flex, than it is to use a large, heavy guide scope that’s likely going to add flex somewhere.