SharpStar 100QII f/5.8 Quadruplet APO Astrograph

[nephilim]

Hi,
I have my eye on the above scope  https://www.firstlightoptics.com/sharpstar-telescopes/sharpstar-100qii-f5-8-quadruplet-apo-astrograph-telescope.html for some winter galaxy AP & was wondering if anyone has this scope & is it worth the price? (Also would it suit my ASI533MC-Pro?) I'm particularly drawn to the fact that I wont need to faff with backfocus when changing filters. Am I correct in thinking that a quadruplet doesn't need a flattener or is that just wishful thinking?
Any images taken with this scope would be much appreciated.

Thanks

Steve

Edited August 11, 2021 by nephilim

[GalaxyGael]

Hi Steve,

I guess my reply to you is my first post!

I had the 86SDQ version of these scopes. Great in principle but here is my advice. In my case, it suited the asi1600 with 1.4"/pixel as far as I recall. The 533 has the 3.76 um pixels so you're at slightly better resolution at the longer focal length (mine was 464 mm). Its a nice combination for a square smallish sensor size. You might be able to get away with flats and darks for a while.

Ask for a bench test before shipping, although FLO will likely do one?.  Mine had pinched optics in the main cell, and these are made a little better than before so the lens cell is not a twist off, but a series of push-pull screws that I did not want to play with.

Focuser is excellent, although a little backlash in the fine focus I found. Check too that none of the oil or adhesive moved onto the lenses. It did in my case so I assume that lens installation is common to these models. Now, I may have had several unusual one-offs all happening at the same time to be fair. 

Color correction is fine, but mine was FCD100, not quite as good as FPL53 and its was a pair of doublets instead of a triplet with single lens inbuilt corrector. I found blue/red fringing on many stars, especially if low in the horizon, and is common with these petzvals.

One good alternative is the 94 EDPH with flattener. Considerably cheaper and runs at f/4.4. with 414 focal length, maybe that is too wide for you? Good reviews of this model too out there.

Petzvals handy though, and I have a TS version of the 71 f/4.9 that is really good and flat. It too had pinched optics, so definitely get the bench test at FLO for peace of mind whichever you go for. 

[nephilim]

1 hour ago, GalaxyGael said:

Hi Steve,

I guess my reply to you is my first post!

I had the 86SDQ version of these scopes. Great in principle but here is my advice. In my case, it suited the asi1600 with 1.4"/pixel as far as I recall. The 533 has the 3.76 um pixels so you're at slightly better resolution at the longer focal length (mine was 464 mm). Its a nice combination for a square smallish sensor size. You might be able to get away with flats and darks for a while.

Ask for a bench test before shipping, although FLO will likely do one?.  Mine had pinched optics in the main cell, and these are made a little better than before so the lens cell is not a twist off, but a series of push-pull screws that I did not want to play with.

Focuser is excellent, although a little backlash in the fine focus I found. Check too that none of the oil or adhesive moved onto the lenses. It did in my case so I assume that lens installation is common to these models. Now, I may have had several unusual one-offs all happening at the same time to be fair. 

Color correction is fine, but mine was FCD100, not quite as good as FPL53 and its was a pair of doublets instead of a triplet with single lens inbuilt corrector. I found blue/red fringing on many stars, especially if low in the horizon, and is common with these petzvals.

One good alternative is the 94 EDPH with flattener. Considerably cheaper and runs at f/4.4. with 414 focal length, maybe that is too wide for you? Good reviews of this model too out there.

Petzvals handy though, and I have a TS version of the 71 f/4.9 that is really good and flat. It too had pinched optics, so definitely get the bench test at FLO for peace of mind whichever you go for. 

@GalaxyGael Hi,  thanks very much for such good info. I'd read a thread on CN re pinched optics although it was from a while back. I'll definitely ask FLO to carry our a bench test etc. A Fl of just over 500mm is what I'm after really for the likes of the Leo Triplet etc, I think @414 mm the EDPH is a little too wide although it's certainly one to keep in mind.

I've a month or so of saving to do & also to continue looking at all other options around this quality & price point.

steve