Another Plate Solution Problem

Reggie Jones

Hi Adam; after numerous attempts which include rewatching your plate solution video(s) several times, I'm at a loss to understand what I'm missing.  This is an image of Sh2-119, the Clamshell nebula.  It was taken via Telescope Live on the Takahashi FSQ-106EDX refractor and QHY 600M camera.  The refractor has a 382 mm focal length but it has a 0.73 focal reducer attached, shortening the focal length to 278.86 mm.  The camera's pixel size is 3.76 microns making the plate scale 2.78 "/px.  The camera sensor size is 9380 x 6172.

Long story short, I've triple checked the image coordinates of the frame using Aladin as you recommended and when Image Solver runs (screenshot attached), it will show 4000000 possible solutions which I know from experience is an infinite loop and I have to restart the process.  Not sure where to go from here.  I'd like to get a plate solution so that I can use SPCC to get color calibration of the stars in this narrowband image.

Here is a link to the image I'm trying to solve:  https://www.dropbox.com/scl/fo/4a221731fbhbdg3dgt2fj/h?rlkey=qn488dj1i450dkf8j1r4umgj7&dl=0

Hoping to learn what I've missed.  Thanks in advance - Reggie Jones

Mike Cranfield

The Takahashi FSQ-106EDX has a focal length of 530mm so with the 0.73 focal reducer we have 387mm. If you use this in ImageSolver your image solves fine.

Reggie Jones

Thanks Mike - according to the TL website, they show the focal length as 382 mm (attached).  I'll communicate to them and have them correct this info.

Reggie

Mike Cranfield

I think they may have quoted the FL with the reducer in place.

Reggie Jones

Yea, I went back and looked at that.  If you calculate the focal ratio shown (3.6) that they do say is with the focal reducer, then you come up with the 382 mm.  The 382 mm listed as the focal length doesn't specifically say that it is with the focal reducer in place, so I used that as the native focal length and recalculated from there.  I've sent them a note asking them to add that the 382 mm focal length is with the focal reducer.

Reggie Jones

Mike, can you show me the settings you used to solve the image?  I'm still having trouble getting it to solve.

Thanks

Mike Cranfield

I have placed an Image Solver instance .xpsm file in dropbox here. This works fine for me.

CS, Mike

Reggie Jones

Thanks!

BlockHead

I swear I demonstrated this with some TL data recently and made a video on it.

Reggie... you should look at the set of videos that come up when you search for plate solution or image solver.

I make too many videos...too many questions. lol

The main take away is that any time a focal reducer is in place...the focal length (quote or calculate from published values) is just an estimate. You need to undertstand if they are stating the effective FL or just the native FL. The effective FL is just an estimate though...because in many instances spacing of reducers matters.

-the Blockhead

Reggie Jones

Thanks Adam. You did do a video on all of this which I watched several times working through this issue and I did finally get it solved. I’ve also asked Telescope Live to look into how they are stating this. Reggie