A few questions on plate solving with MaximDL

adman (Adam) · #1 06-09-2011, 09:00 AM

with the clear but moonlit skies last night I decided to investigate plate solving with MaximDL - something I have been meaning to do for a while. Now - I am still in the early stage of using Maxim DL, and think that I will eventually switch over to using it for guiding as well.

I got it to solve frames from my QHY5 very nicely (couldn't believe how quick it was on my little netbook) - although I did need to reduce the magnitude stars it would try to use from 20 --> 12. Maxim also picked up the position of the mount without any issues, and I was able to use that for the rough position. I was also able to sync on the solved position, and also slew to other stars shown in the 'Zoom' tab (found the Helix for the first time, and snapped a couple of frames of that just for the hell of it - I think it needs more focal length than my FS-60 with a reducer though

)

First question is - when it has solved the image and gives you the position, it also gives you what it thinks is the focal length and image scale of your scope/camera etc. When I used the calculator it provides to figure out the image scale - it gave me 4.76 or something like that (355mm focal length FS-60 with 0.72x reducer = 255mm, then 5.2 micron square pixels in QHY5), but after solving it said the image scale was 3.03 or therabouts - can't remember the exact numbers. Why the difference, or is my focal length / pixel size wrong?

Second question: does syncing the mount with the solved position have the same effect as doing an alignment using the handset, or syncing stars with CdC? And if you sync multiple stars using MaximDL, does it build a model using all of the stars or does it only 'remember' the current one?

Third question: what other cool stuff can I do now I have the basics sorted out?

Cheers
Adam

RickS (Rick) · #2 06-09-2011, 09:22 AM

G'day Adam,

First question: dunno, it always seems to get the image scale right for me. 3.0x seems about the right image scale without the reducer. I wonder if that's a coincidence? Have you set the correct (reduced) focal length in Maxim?

Second question: on my mount a sync is a sync no matter where you do it (unless you tick the box that says to convert a software sync to a recalibrate!) The last sync is the only one that is remembered.

Third question: you should be able to overlay an image on the observatory zoom window now and calibrate to use auto center.

Cheers,
Rick.

adman (Adam) · #3 06-09-2011, 09:51 AM

Quote:

Originally Posted by RickS

G'day Adam,

First question: dunno, it always seems to get the image scale right for me. 3.0x seems about the right image scale without the reducer. I wonder if that's a coincidence? Have you set the correct (reduced) focal length in Maxim?

Thanks Rick, I have just checked it with Ron Wodaski's CCDCalc - and I get 4.2 arcsec/pixel with the reducer. I was pretty sure that I entered in 255mm for the focal length - buuut - it was late so anything is possible. Although surely the focal length it calculates from the image after solving should be correct??

Quote:

Originally Posted by RickS

Second question: on my mount a sync is a sync no matter where you do it (unless you tick the box that says to convert a software sync to a recalibrate!) The last sync is the only one that is remembered.

ok

Quote:

Originally Posted by RickS

Third question: you should be able to overlay an image on the observatory zoom window now and calibrate to use auto center.

hmm.....what? Can you repeat that more slowly for the intellectually challenged among us (ie: me!)

Adam

DavidTrap (David) · #4 06-09-2011, 10:12 AM

Adam,

I have had similar queries about the calculated focal length being different from what is written on the scope. From what I undersand, the software gets the pixel size from the driver for your camera (read that bit in the help file). I presume it then calculates the focal length backwards from that using the pixel size and position of stars on the image. My 2000mm SCT is 2222mm according to plate solving from Maxim.

The amount of "reduction" your reducer provides is dependant on the distance between the reducer and the imaging plane. Small changes can have significant effects on that reduction and hence the effective focal length.

Under the observatory button on Maxim there is a catalogue and sky view - apparently you can overlay your image onto that sky view. I guess it might help with composition of shots.

Other cool thing about having plate solving working is coming back to an image on a subsequent night. You take an image, plate solve that and sync your mount. Then you open up a previous image, plate solve it and tell your mount to "goto" the centre of that image. Now you can shoot the same field of view night after night. The plate solve also gives you an "angle" in case you've rotated the camera for composition - therefore you can match that angle again on subsequent nights.

DT

adman (Adam) · #5 06-09-2011, 10:32 AM

Quote:

Originally Posted by DavidTrap

Adam,

I have had similar queries about the calculated focal length being different from what is written on the scope. From what I undersand, the software gets the pixel size from the driver for your camera (read that bit in the help file). I presume it then calculates the focal length backwards from that using the pixel size and position of stars on the image. My 2000mm SCT is 2222mm according to plate solving from Maxim.

I am using my QHY5 guider to provide the image - do you know whether these use the FITS format that maxim can read, or is it something else. Also - is there a way of using my DSLR to provide the image to solve - because my guidscope and imaging scope are not perfectly aligned, and I am not using guide rings - they are both in fixed rings, so it will be a bit of a challenge to get them perfectly lined up.

The amount of "reduction" your reducer provides is dependant on the distance between the reducer and the imaging plane. Small changes can have significant effects on that reduction and hence the effective focal length.

Under the observatory button on Maxim there is a catalogue and sky view - apparently you can overlay your image onto that sky view. I guess it might help with composition of shots.

Quote:

Originally Posted by DavidTrap

Other cool thing about having plate solving working is coming back to an image on a subsequent night. You take an image, plate solve that and sync your mount. Then you open up a previous image, plate solve it and tell your mount to "goto" the centre of that image. Now you can shoot the same field of view night after night. The plate solve also gives you an "angle" in case you've rotated the camera for composition - therefore you can match that angle again on subsequent nights.

Now THAT is cool - I am going to try that!

Adam

RickS (Rick) · #6 06-09-2011, 11:58 AM

Quote:

Originally Posted by RickS

Third question: you should be able to overlay an image on the observatory zoom window now and calibrate to use auto center.

More detail:

From the Observatory window Zoom tab click on Options and you'll see an Overlay Image in the list. If you click on this it will overlay the selected (and plate solved) image on the displayed map. I find this useful as a composition aid.

In the Observatory window Telescope tab there's a Center on Image section. If you Calibrate using the PinPoint option you can right click on a point in an image and recentre on that point.

As David said, the ability to plate solve a previously taken image and return to that exact field is very useful. Unfortunately, the Image Center from PinPoint button crashes my Maxim so I have to copy and paste the RA and Dec manually.

Cheers,
Rick.

adman (Adam) · #7 06-09-2011, 01:45 PM

Thanks for that Rick

Adam

Octane (Humayun) · #8 06-09-2011, 02:26 PM

Adam,

I have written a mini tutorial on how to re-centre a target night after night.

I will post it when I get home.

PinPoint is tres cool.

H

adman (Adam) · #9 06-09-2011, 02:41 PM

thanks H - I'll look out for it

Adam

DavidTrap (David) · #10 06-09-2011, 07:16 PM

Should be no problems using data from your DSLR - I did with a 350D - beauty of using Maxim is the ability to record FITS files from DSLR.

Fairly sure data from QHY5 is FIT format too.

DT

White Rabbit · #11 09-09-2011, 01:10 PM

Hi Guys.

I need to get this going as well. Have maxim DL and maxpoint is but max point uses pinpoint LE, would I be better off ditching Maxpoint and getting pin point.

If theres no real difference then i wont bother as I've already spent $180 on maxpoint. I dont mind dropping the extra cash if point point is the way to go but obviously i'd preferr not to.

DavidTrap (David) · #12 09-09-2011, 02:44 PM

Pinpoint LE comes with Maxim. Have a read of the help file - fairly self explanatory on what you need to do. There is a 300mb catalogue file that you need to download to get it working.

DT