Testing the Fluorostar 91 in Messier 101 widefield (Paul Macklin)

Testing the Fluorostar 91 in Messier 101 widefield

I think I've got my new William Optics Fluorostar 91 just about dialed in! I tested widefield in nearly full moon conditions, so please excuse the poor quality.

I'm using the W.O. 0.8x flattener, a ZWO OAG, ZWO filter drawer, and a new asi2600mc-pro. Setting the WO reducer at 5.6mm is a good start, but it doesn't account for the thickness of the filter. At that setting, I had some star elongation in the corners and some evidence of tilt.

Adjusting the flattener to 6.0mm fixed the corners, and the modest tilt was also corrected. My OAG stalk is still causing slight shadow that can *mostly* be resolved with flats, but you can still see some artifacts from that here. Next time I'll pull it up even a little bit more.

Still this is all looking good for my widefield upgrade from the ZenithStar 61ii. More aperture, greater pixel resolution (from 2.15"/px at f/5.9 to 1.8"/px at f/4.72), without sacrificing FOV due to the larger sensor on the new asi2600mc-pro (upgrading from an asi533mc-pro). Now I just need to transfer my EAF from the ZS to the FLT. I think we have a winner!

The full setup is about 17 pounds. OAG-based guiding (with just the zwo OAG and a wee asi120mm-mini) has been under 0.8" RMS on both axes--well below my pixel scale. This is in spite of very poor balancing since I only had a 10 pound counterweight and don't have started z-axis balancing yet. So, this scope is indeed quite viable on a cem26.

Prior widefield setup: ZenithStar 61 + asi533mc pro
* aperture: 61mm
* optics: doublet APO FPL-53
* FOV: 1 deg 48' x 1 deg 48'
* resolution: 2.15"/px at f/5.9

New widefield setup: FluoroStar 91 + asi2600mc pro
* aperture: 91mmm
* optics: triplet APO FPL-53
* FOV: 3 deg 7' x 2 deg 5'
* resolution" 1.79"/px at f/4.7

Better and faster optics, wider FOV, and finer resolution. That's a win!

Final
Original
B
C
D

B

Title: Zoom on NGC5474

Description: Zoom in on NGC5474 -- a top-down spiral galaxy.

Uploaded: ...

C

Title: Zoom on NGC5422

Description: Zoom on NGC5422, an edge-on spiral galaxy.

Uploaded: ...

D

Title: asi533mc simulated crop

Description: Here's a crop to the approximate FOV of an asi533mc pro for comparison.

Uploaded: ...

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Status	Advanced success
Started	...
Astrometry.net job	5678716
PixInsight job	2B7TF1G53NLGLVRNO0Q1RXY7735DI8KO
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	14h03m11s.46
RA (top/left)	13h52m47s.34
RA (top/right)	14h13m28s.29
RA (bottom/right)	14h14m06s.64
RA (bottom/left)	13h52m22s.90

Dec (center)	+54°20′48″.9
Dec (top/left)	+53°17′51″.6
Dec (top/right)	+53°16′28″.2
Dec (bottom/right)	+55°20′05″.3
Dec (bottom/left)	+55°21′39″.8

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