Sort of imaging

[Calculad]

I am returning to photometry and my guide requirements are (compared to imaging) pretty low.

I have to keep a stellar image inside a 2' graticle for 10 seconds. On my last telescope (8" Newt Refl) I did not need to guide my equatorial mount.

Wind was generally my biggest problem.

To the question. I am tempted by the Celestron AVX11 telescope and mount:

https://www.365astronomy.com/celestron-advanced-vx-11-schmidt-cassegrain-computerised-telescope

Most reviewers (astrophotographers) advise that this system is not up to astrophotography. As you can see I think my requirements are

less stringent than imaging, but I await any advice offered on this mount. The increased light grasp would help my photon counts. The 11" f10 Celestron would reduce the graticle to just over 1' of arc.

Thanks for reading.

[Cosmic Geoff]

24 minutes ago, Calculad said:

Most reviewers (astrophotographers) advise that this system is not up to astrophotography. As you can see I think my requirements are

Depends what kind of astrophotography you have in mind.  Some people use Schmidt-cassegrains for imaging small galaxies and the like. Also great for planets. (Smaller aperture refractors are considered more user-friendly than a big SCT for astrophotography.)

Some might think that an 11" SCT is under-mounted on an AVX. I suggest seeking further advice.

Keeping a stellar image inside a 2' (two minutes of arc?) for 10 seconds does not seem an exacting requirement for a GoTo mount. I think my GoTo mounts perform much better than that.

[newbie alert]

What type of imaging are you looking to do? I'd say either deepsky or planetary the avx with a 11 inch tube at f10 is under mounted for deepsky, boarder line for planetary.. if you plan to use it for deepsky then I'd suggest you do some research as imaging with a SCT isn't as easy as using a widefied frac.... How much signal are you going to collect in 10 secs subs.. must be something really bright

[ollypenrice]

I agree that 2 minutes of arc is not a big ask. I think an EQ6, unguided, might have an error of 30" of arc, or so. Is your exposure ruined by being briefly lost from the slit? I know nothing about photometry.

Olly

[robin_astro]

What sort of photometry are you doing that requires just keeping the star within a 1-2 arcmin box ? (Photo electric photometry (PEP) perhaps, though I know nothing about it).  Most photometry these days is done by measuring from images where the star image has to kept be moderately tight and round eg within say a few arcsec at most during the exposure.

(Perhaps best moved to the variable stars subforum ?)

Cheers

Robin

[robin_astro]

8 minutes ago, robin_astro said:

 (Photo electric photometry (PEP) perhaps, though I know nothing about it)

If that is the case then PEP photometrists are pretty rare animals these days. The AAVSO PEP section would probably be your best bet for advice

https://www.aavso.org/aavso-photoelectric-photometry-pep-section

Cheers

Robin

[Calculad]

Thanks for the useful replies. I'll answer the questions.

There is no imaging involved. The photometer counts over 10 sec on the star then 10sec on the sky to subtract. Also on comparison and check stars to get a differential mag. Sounds complicated but it's much less so than CCD IMHO. I'm a bit too old to change to that now.

I used to be able to get sufficiently high counts about 7th mag with my old 8" (20cm) Newtonian.

The reason for the increased size is to maybe push this a bit fainter.

I also wanted a visual instrument for a bit of interest for the grandchildren. So there's a compromise going on here too.

I think I need to strap the photometer on one and try it. I have tried to contact amateurs in the Brighton area but had no replies sadly.