First light with the nice new gear!
What else but my favourite nebula, ngc 6188 - "Fighting Dragons of Ara".
I have imaged this beauty with almost every 'scope I've owned, but it's never looked so sharp!
Still messing about with the correct spacing for the 0.7 Tak reducer, (might be a spot of tilt there too?).
I've been working on the spacing to get round stars across the field in 1mm increments to get to this point, but might need to go testing again in 0.5 mm steps or even finer!
Only one night's data so far - Hope to add more O3, S2 & RGB as soon as the skies clear again!
Given that this was taken under a FULL MOON from suburban Melbourne, I'm pretty impressed by my new Chroma filters too!
(better value than Astrodon, parfocal & amazing quality)
Takahashi TOA 130 + Reducer 0.7
(spacing is almost right, just missed it by thaaaaat much in the cnrs)
QSI 6162 WSG8 Camera - nice!
Chroma 5nm Ha & 3nm O3 Filters - 3 hrs each 1200sec subs
Takahashi NJP mount
Lots of persistence & fiddling about....still a WIP!
Wow a great first shot with the new rig, well done!
Since I hope to have a similar rig in the not so distant future (toa130 + qhy16200a), what is your process to get back spacing just right? I assume start with what you think it is based on manufactures specs and take a shot, analyze then add spacing rings and shoot again (rinse and repeat until right)?
Looks good. Massive field. Once you have that corrector sorted out you'll have a killer rig.
Cheers Marc, yes I’m truly amazed how ‘Taksharp’ (sorry) the stars are and the resolution of the star cluster HR 6187 into several tiny but separate stars is impressive. So too is the detail of the “rocking horse” on the Ara wall itself.
Guess that’s why these Taks are up there with AP’s as the ‘Rolls Royce’ of refractors. This reducer spacing is indeed challenging though. Not much is forgiven with the large sensor on this nice new camera!
Quote:
Originally Posted by Xeteth
Wow a great first shot with the new rig, well done!
Since I hope to have a similar rig in the not so distant future (toa130 + qhy16200a), what is your process to get back spacing just right? I assume start with what you think it is based on manufactures specs and take a shot, analyze then add spacing rings and shoot again (rinse and repeat until right)?
David thanks yes you are correct that’s been my method and although I’m using hand crafted variable spacers & locking rings to fine tune the cnr stars, it’s a time consuming process! I’ll get there eventually
Anacortes has a table with the spacings for various models. You need the exact metal back distance for that reducer. It should be in their table. I have found them to be very accurate in the past.
Sure there are some technical quibbles, but for a first light image it's an absolute ripper
I really like the fact the "Stallion" of Ara is nicely resolved. Too often lost in the haze in lesser renditions.
Nice
Hi & thanks Peter, I was reasonably happy with this as a test pic, but can’t wait to see what this thing can do when it’s fully dialed in! I was very aware that Ara experts like yourself would zero in on the Stallion - glad it passed the test! (Phew!) lol
Quote:
Originally Posted by gregbradley
A wonderful first light. You must be thrilled.
Anacortes has a table with the spacings for various models. You need the exact metal back distance for that reducer. It should be in their table. I have found them to be very accurate in the past.
It looks like a small amount of tilt as well as the stars are not distorted to the same degree in each corner.
Greg.
Thanks heaps Greg, yes I’m as exited as a kid in a candy store that I can play with such nice toys!
I appreciate the links there- will see what I can do.
The camera is very heavy though, might need some expert fine tuning to negate that tilt issue yet!
Hi & thanks Peter, I was reasonably happy with this as a test pic, but can’t wait to see what this thing can do when it’s fully dialed in! I was very aware that Ara experts like yourself would zero in on the Stallion - glad it passed the test! (Phew!) lol
Thanks heaps Greg, yes I’m as exited as a kid in a candy store that I can play with such nice toys!
I appreciate the links there- will see what I can do.
The camera is very heavy though, might need some expert fine tuning to negate that tilt issue yet!
Now I have my own procedure I fix tilt in about 10 minutes.
Best to simply get those spark plug spacer set from Supercheap Auto.
Work which is the offending corner(s) and install a spacer between the camera and the filter wheel or the filter wheel and the focuser whichever allows you to do it. Looking at that image its probably something fine like a 18mm spacer.
Now I have my own procedure I fix tilt in about 10 minutes.
Best to simply get those spark plug spacer set from Supercheap Auto.
Work which is the offending corner(s) and install a spacer between the camera and the filter wheel or the filter wheel and the focuser whichever allows you to do it. Looking at that image its probably something fine like a 18mm spacer.
In your case you would need to correct the metal back distance of your reducer and get it to 71.5mm. Make sure you allow for the thickness of the filters correctly. If they are 3mm you add 1mm (1/3rd) to your overall spacing.
1. Take focus image of an area of stars and focus the image (perhaps just focus the centre stars)
2. Examine all 4 corners and sides. Are they all in focus, tight looking and round? An in focus image looks a certain way. I am sure you know what it looks like. It has a tight look for want of a better word. I have learned to recognise that exact point but software that uses graphs is what I normally use (the old CCDsoft).
3. Let's say the top right corner has bloated stars perhaps a bit elongated as well but the other 3 corners are tight looking.
4. Determine the orientation of the image to your physical camera.
Standing behind your scope's camera the image displayed on your computer is reversed up and down and left and right. So top left in the image is bottom right on your camera looking at it from behind.
I loosen my camera where it attaches to the filter wheel (you will need some point where you can insert the packer then retighten or invest in a tllt adapter - Teleskop Services has serveral and Gerd Neuman has a nice one but expensive).
It will require a thinner packer than you might imagine. Try a thin one like .18mm.
Tighten up, refocuc and take another focus image. I use 2x2 binning to speed it up plus the faster download speed. But once you have it finish on 1x1 for maximum accuracy.
Is it better or worse or the same? It should be better. Check the other 3 corners. Sometimes you pack it the whole side as the whole side is off.
So repeat and get the packing right until its good on all 4 corners after refocusing.
If you find you have a lot of packing in one corner, start again, you went off the rails. Its usually only a smallish packer with these large sensors.
Once you got it right make a night using Windows notebook and save it on your computer so you know next time if you remove the camera or swap cameras. I tape the packer to my Proline so it stays in place even if I swap it out to another scope.
Tilt is not necessarily in the sensor, although that would be a source. It can be not quite square adapters, dovetail adapters for example can lock in slightly off the groove.
Flex is a different issue and if its flex then that would require stronger everything and tightening the focuser up etc. Flex seems to be more of an issue for Newts etc not refractors which are easy to handle.
Looks like you’re getting it coming along there Andy
Spacer wise it appears that you’re maybe 2mm away given that it has larger 6 micron pixels and it’s APS-H and not FF.
You have some tilt between the top/bottom and left/right which is evident in the bottom left corner which has more out of focus look than aberration.
Although there is a lot of nice detail many of the smaller stars look a bit blobby. Focus maybe? Or possibly even artefacts of star removal?
The first thing that jumped out at me in the test subs was the way HR6187 was resolved.
If you go looking for thin spacers at supercheap etc, the second link you put up Andy is what you need. If you ask for a "Feeler gauge" set they will know what you are talking about.
Looking at the full res image, I think that tilt and spacing adjustments may not be enough to get all four corners the same. I think there is some eccentricity error in there as well. You will have to determine, as a first step, if that is coming from the objective or from the field corrector.
Thanks All - Here is a pic of all the variable adapters including a 17mm spacer that I have to connect the camera to the reducer & flattener and FT focuser.
There's an assembled set pictured here with the flattener.
EDIT: Added a pic of the reducer with 17mm spacer. The spacer screws onto the reducer and requires a threaded adapter at the other end to mate it to the camera. (See pic of reducer, threaded adapter & assembled OTA, this configuration is approx 19mm).
The backfocus for the reducer was calculated from the mating surface of the reducer to the QSI 6162 front adapter plate.
Tak TOA 130 (with this model reducer) specifications = 83.7mm
QSI 6162 camera with OAG module & camera adapter = 51mm to OAG face + 14mm camera adapter = 65mm
Therefore spacing between reducer & camera =18.7mm
This is quite tricky to get right with the variable threads!
For those who have an aptitude for this - here is a dropbox link to star test shots taken with spacing in 1mm increments from 14mm >22mm. The consensus seems to be that 17mm was the best so far.
With the 17mm spacer in place the system supposedly becomes f5.76 instead of f6.0 but the tradeoff is a smaller corrected image circle and yet more calculations to determine the correct spacing!
As everything is screw threaded, I'm not sure where exactly I can insert the feeler gauges into the imaging train?
The TOA-67 flattener is somewhat easier, allowing for optimal backfocus @ 106.2mm
QSI 6162 +OAG+Adapter = 65mm
therefore spacing between flattener & camera is 41.2mm
However, I have not tested this combo as yet.
I don't think that is right Andy and it may be why the stars are off.
Per the link the correct metal back distance is 71.5mm,
scroll down the page and you'll see it. Where did you get 83.7mm?
I think there might be more than one TOA reducer, not 100% sure.
