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I've had some success with EQMod over the last couple of days and am now looking to get as accurate star alignment as I can.
I understand that platesolving is a great way to centre and correct with star alignment and have been following the tutorial shown here.
Annoyingly, I can't open AstroTortilla despite uninstalling and reinstalling I'm always presented with a dialogue box stating:
"The logfile 'C\program Files (x86)\AstroTortilla.exe.log' could not be opened: [Errno 13] Permission denied: 'C:\\Program Files (x86)\\AstroTortilla\\AstroTortilla.exe.log'".
I've tried to run this as administrator from program files which gives me the following dialogue:
"See the logfile 'C:\Program Files (x86)\AstroTortilla\AstroTortilla.exe.log'
This file does not exist.
Has anyone had this issue before? I've run a search on Google for the error as outlined below but I can't see anyone else has had this specific error.
I run a Youtube Channel and as part of that I like to live stream the telescope. But the problem is lack of consistency.
Orion EON 110, Meade 10" SCT
Orion Mount - Exos2-PMC. Meade Mount 'push to' alt az with clockwork drive
APT, SharpCap, PHD2, Stellarium, ASCOM Hub
Focal Lengths Orion 660mm, Guide Scopes 188mm, SCT 2500mm
Powered USB for ZWO cameras (120 and 294)
Here is what happens:
Cameras, sometimes work, sometimes don't. I am not making the mistake of trying to get APT and SharpCap to view the same camera. I used APT for the guide scope and SharpCap for the main tube and the 294. Sometimes APT will take an image, sometimes it will do live view, sometimes both, sometimes neither. It is very distracting to the stream to spend an HOUR turning the computer off and on, plugging, unplugging and replugging the cameras just to get them to image.
When I do get an image it plate solves at the NCP, but if you move away, setting the coordinates to the scope position or the object I am looking at, it doesn't consistently plate solve. Sometimes it does, sometimes not. It is completely irregular and can change within a session.
Not all three plate solving means even work, for blind solve,
ASTAP never seems to work, either in point craft or locally stand alone
PS2 and ASPS work intermittently, as above
I did download all the catalogs and they are in the default directories.
This is very frustrating and I was wondering if anyone else is having this issue or has suggestions.
Celestron's EdgeHD product line features an integrated field flattener. As with all flatteners, these produce optimal results when the imaging plane is a specific distance from the flattener. In the EdgeHD whitepaper Celestron describe the optimal backfocus of 133.35mm (5.25") for the 8" model, and 146.05 (5.75") for the 9.25", 11" and 14" models. They suggest that the image plane should be placed within 0.5mm of this distance.
When putting together an imaging train it can be quite hard to determine the actual backfocus. You could add together all the optical lengths quoted by manufacturers, you could get calipers and actually measure each part or even try to measure the entire thing (although it can be quite hard to figure out where to measure from. At some point, you have to trust some manufacturer spec (unless you fancy risking your sensor).
Once all this is done you might, however, find that things vary ever so slightly; everything from the tightness of threads to the T-ring not quite giving exactly 55mm. How do you work out if you've done it all correctly?
In a table in the whitepaper (page 13), focal lengths are given for each OTA (for example 2125mm for the 8" model). Hypothetically then, it should be possible to measure whether or not you're at optimal backfocus by plate solving for your image scale. In the same table, an image scale is given for a sensor with pixel size 6.4 micron but you can use a calculator (such at the astronomy.tools one) to work out the expected image scale for your particular sensor. This does require that your image is as close to perfect focus as possible.
Putting all this into practice. I used my calipers to try to get the image train as close to 133.35mm as I could and then plate solved some resulting data taken with a DSLR with 5 micron pixels. From my calculations, if I'm in focus at the correct spacing, I should have an image scale of 0.485"/pixel.
However, my astrometry.net solves gave an image scale of 0.495"/pixel. Working backwards, this indicates that I was at a focal length of 2083mm, quite a way inside 2125mm. Although I can't find a reference I've read that, for an SCT, the focal length changes by approximately 3mm for each 1mm of backfocus, this implies that my sensor is 14mm too close!
Now, I'm no expert with calipers but I feel like I couldn't have been more than a few mm out, and if anything I thought I was too far. I suppose I could have been a bit out of focus but surely not ~10mm.
Is there a mistake in my logic of aiming for 2125mm focal length?
The other night, I got a rather weird thing happen using Sharpcap. In live-stacking, the first image arrived and it was full of stars. So, without changing any settings, I did a "platesolve" (which also realigns the scope) to centralise my target. It did its single frame capture and I got a practically blank screen and a message saying it could only detect 3 stars. I tried reducing the "sigma" setting, as advised by the on-screen message, with little effect. What gets me is that the same settings produced a whole mass of stars in each of the subs that were being live-stacked. Never had this happen to me before, and no, of course I didn't do anything intelligent like saving the log file!
I can always try to replicate this next time (although I always find trying to replicate something that isn't working to be a weird activity in itself!), but on the off-chance that anyone can see what was happening without the log file, I thought I would ask.
I don't have a goto mount and I wondered if there was just a simple way of showing where the scope is pointing on (for example) stellarium or kstars.
I try and star hop to where I want to go and in the depths of the garden (or remote) I don't have any wifi to run nova.astrometry. so Im looking for a platesolving app that can run standalone on a windows laptop.
Usually I get to where I want to see, but sometimes I just get lost so Im looking for something that will help confirm or show where I have ended up so that I can manually adjust the scope to get where I want.
A typical use case would be....
Locate bright star near target.
Check collimation of camera, finder, telephoto (with dslr or gpcam + startcap)
Move/starhop to target.
… check whats supposed to be in the finder
… mhh its not there.
-- reverse steps and try again.
… mhh its still not there
check Im at the right start, double check target position and and try again
… mmmh still not there
Then what I want to do is
* take a photo and platesolve to find out where Im actually looking at this time
* correct manually using slow mo or some more star hopping
* hopefully get to the target, and enjoy the view.
Ive tried loading up 'all sky platesolver' which I can get to solve and give me location RA and DEC, but then I cant see how to get that location just to show on a star map.
Also I cant get any images to show on the screen from allskyplatesolver (although it says it should - image get not-found type error)
I don't really care what star map I use. I don't really want to start copying and pasting ra and dec into scripts at 3am.
The details of the platesolving apps seem to be mainly focussed on driving a mount to a location, whereas I just want to confirm where I've ended up pointing on a map so I can do the correction myself.
Any help please ?
PS - I might be trying to do this at 3am in a grassy field with the laptop balanced on an upturned crate whilst doing this ?