msacco

6 minutes ago, iapa said:

I have a micro USB powered stick PC, that has 1.4GHz Z8530, with 4GB RAM running Win10 Pro (it was £15 for an OEM license from Amazon) and a 64G solid state storage.

This handles SGPro, and PHD2, focus motor control for both guide and imaging scope, and the Pegasus pocket powerbox.

Files are saved to a OneDrive folder so I can access from a PC in the house.

I'm currently trying a raspberry pi, I'm using a custom distro which I can't really say which here, but so far it works amazingly. I think that if I were to go the windows route, I'd probably get a mini PC with 8GB ram as Win10 is quite a hungry system.

On 07/05/2020 at 20:07, iapa said:

Olly,

I found an old article by your good self

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwjY_7LRnaLpAhXzmFwKHWXgBGQQFjAAegQIBBAB&url=https%3A%2F%2Fstargazerslounge.com%2Ftopic%2F264094-artificial-star-alternative-method%2F&usg=AOvVaw0AHOGMbL6P0JmpwnjpNw62

one post mentions distances

I guess I'll give it a short sometime, thanks!

Do you know if there is any size required?

12 hours ago, ollypenrice said:

I don't know it either. I've used the Picostar artificial star which is OK.

Olly

Way too expensive though

11 minutes ago, ollypenrice said:

Take a shiny new ballbearing and a decent sized old cardboard box. Spray the box mat black on the inside and glue the BB to the bottom. Set this up at a good distance from the scope so that the scope looks into the box at the BB. (There is a formula for how far away it should be but I can't remember it and got decent results from too close. It would google. The length of a decent driveway ought to do it.) Illuminate the BB with a torch beam, or whatever, just off axis.

The BB test is to be found in some of the best optical shops in the world. I saw it in Dany Cardoen's workshop down the road from my place and he has mirrors at Paranal. The principle is delightfully simple: only light from the part of the BB closest to the scope will be reflected towards the scope, so it approximates automatically to a point source. It isn't as fine as a star test but it's a very good start.

The problem is, with the Hyperstar, that you can only collimate with the camera and F2 is pretty darned difficult. I've commented on Starizona's claim that the Hyperstar makes imaging easy elsewhere and loudly!

Olly

Thanks for the comment, I'm actually not really referring to hyperstar here, it is a completely different story, which as you said is not really as easy, but I still need to try it with my new and correct adapter.
I thought of maybe purchasing the Hubble Optics 5-Star Artificial Star(s), but idk if it's worth it...Some says it simply works, but other complains about the quality which is plastic. Don't know ^^

14 hours ago, iapa said:

as an FYI, I added a few more mm to the light train and the stack rowlocks like 

I added in some spacers and the image now looks like this

curvature reduced from 65% to 42%

not that's relevant but, total tilt is lower, but that's more likely to be the reattaching of everything

That is very interesting, thanks

10 minutes ago, Skipper Billy said:

A spot of dark red nail varnish over the light works wonders - dims it but still visible in the dark.

Holy..........That sounds so simple, yet so brilliant. I'll surely give it a try. Thanks!

9 minutes ago, Dr_Ju_ju said:

Where you see the holes in the body side, you insert a small screwdriver type object and the front rocking part, will 'pop' out, but take care you don't lose the actuator spring.....

As for the replacement resistor value, it will depend on the supply voltage, required light output etc. I used 4K7 resistors, but then I also have loads of them....

I managed to open that, there's thing weird metal piece thing which I'm not really sure where it should go back, I don't see any normal place for it to fit well.

Do you remember where it should go?

Just now, Davey-T said:

Probably have to break one to find out how they're made, hopefully not glued together.

Dave

So it was really easy with a little bit of force, I'm not sure where 1 part should go now though and how to assemble it back ^^

But replacing the resistor seems really easy. Julian, which resistor did you use?

Just now, Davey-T said:

They generally just snap together, I taken similar ones apart and modded them to momentary switches and dimmed the LEDs, not those particular ones so inly way is suck it and see 😁

Dave

So should I just try to disassemble it with force? ^^

5 minutes ago, Dr_Ju_ju said:

Depends on how confident\able you are, as I've also used those switches, but disassembled them & replaced the internal dropper resistor, to limit the light emitted.

A second option would be to use the same style of switch, but then mount an external, (sub)miniature led, suitably set for the brightness you require. 

The first option is very interesting! How would I go about opening the switch and doing that though? Do you have some pictures by any chance? I don't see any screws to open that up.

Hello, I'm planning on making something for field use and I'd like to use switches for it. I previously used the following red switches:

But it seems to me like it outputs too much light, I would prefer a switch with slightest light so I'll be able to know something is turned on, but not so much as these.

Any recommendations? Thanks

6 hours ago, iapa said:

it seems to be a very hit and miss

Need to see if an artificial star can be used to measure this

at least with no astronomical dark, time can be spent on the objectivists stuff

 

Yeah, the only issue is that I don't have an artificial star, and not sure how to make one.

4 minutes ago, iapa said:

I added  few MORE mm between FFR and camera

brought curvature down from 103.3 as measure above to 

64.5%

a big number if probably not good as the image looks better as curvature drops.

Interesting that tilt has changed in X and Y, but over all has gone from 4% to 15%

I think I need to increase distance a bit more

 

 

 

In my next imaging session I'll give this a try and see how it goes, maybe playing with the backfocus could make a difference for me.

34 minutes ago, Xplode said:

Did you verify good collimation with your camera?

I collimated in the field before starting the sequence with everything already setup, it looked really good to me, but again, I'm still not really good at this.

1 minute ago, Xplode said:

Something else to avoud when creating images to check collimation/tilt/etc is low altitudes, especially for color cameras there will be an effect from atmospheric dispersion that could skew the measurements.

By looking at your images it's either tilt or collimation which is the main issue.

You might want to take a startest to check collimation, use Sharpcap with short exposures, defocus a bright star and see how the donut looks.

I've spent around an hour working on collimation, and I really think I got it quite good this time(still not very epxerienced with collimating)

42 minutes ago, Xplode said:

To get images to analyze you should take images of the same spot all the time, i suggest an area without a nebula/galaxy or star cluster, analyze the raw images, not the stacked one.

Use shortish images and make sure they have good guiding.
Don't trust your readings unless you get 5+ images with pretty much the same results, a variance of 5% isn't usual from an image to the next.

 

To check if it's collimation, if possible rotate the camera 180 degrees to see if the abberation rotates with the camera or not.
If it's sag/tilt because of weight check images before and after meridian flip, abberation will rotate 180 degrees.

If you want good input on what the problem is you should upload some of your fits images.

I have found that the numbers on spacing given by the manufaturer is rarely to be trusted, i try to always have spacers to adjust +/- 2mm available.

 

Thanks for the input! How many images should I upload?

I'm meanwhile uploading everything, here is a link: https://drive.google.com/drive/u/1/folders/1UtvWJQREP8sz93EJgDyFksz8G4znrH4b

17 minutes ago, Ricker said:

ASTAP has a free ccd inspector feature. 

Is it increasing the thought of camera tilt?

1 minute ago, iapa said:

Does the EDGE HD eliminate mirror flop that the C8 XLT has? As the OTA changes angle the mirror shifts slightly.

Perhaps the camera is not as secure as you think and is sagging under our friend Gravity?

 

We need someone who knows what they are talking about

 

I'm not really sure about the first part honestly....I'm pretty sure the camera was very secure though.

1 minute ago, Ricker said:

ASTAP has a free ccd inspector feature. 

I'll give it a try, thanks

2 minutes ago, iapa said:

as far as I have reenable to determine - starting for zero knowledge this am - it is most likely to be in the imaging train just because mechanics are not as accurate as a light beam.

If everything was manufactured to sub nanometre tolerances, probability if tilt would be reduced. As it is, one suggestion I have seen is to rotate the camera 180deg.

 

I'll try that! Actually, when trying to think about this more logically, it could make a lot of sense that this is a tilt issue! I've experienced coma for really long time now in many different situations.
With hyperstar for example, I also experienced that, but I had an incorrect adapter which means my back focus wasn't 100% accurate, which with F2 should make a big difference I'd say.

Still, even when I was supposed to be in the correct back focus, it happened. One more thing here is that the coma is mostly in the right side of the image, which is matching the tilt data going from right to left.

Here is the full image:

What I do wonder about though, is why the difference in the tilt is so big between different frames? Even if the mount is moving and somehow affects that a bit, I would not expect such differences?

4 minutes ago, iapa said:

I would suggest that there is an amount of tilt, how much is too much I couldn't say.

You can select multiple images to get an over all measure for your stack

 

 

This seems to be the average result:

So in case there is tilt, why is happens, and how to fix it?

Is it an issue with the camera itself? Or an issue with the way the camera is set up with the gear?

Thanks btw

2 minutes ago, alacant said:

Hi. Yeah, that's good news. The elongation id corner to centre. It it were a corrector, I'd say move it away from the sensor to shorten the aberration. As it's a reducer only, and the ff is a (non adjustable?) part of the optical train already, i'm not certain. A few mm may be all you need. worth a try?

It is totally possible, but I'm not really sure about that...

I'm imaging with the ASI071MC pro, so the backfocus to the sensor itself is 17.5, the reducer requires 105mm of backfocus to the sensor, so that should be:
17.5 + 50(Celestron T adapter), + 35(Extension tube) + 1.2&-1.4(spacer rings) which is equal to 105.1mm. It's 0.1mm more, but with F7 I believe that shouldn't make much of a difference.

Is there any chance that this is not correct?

58 minutes ago, iapa said:

30day free trial

 

Guess the trial was already over for me, but I simply did that in another machine, this is the result I got in a few images(is there any way to get an avg?):

I'm not really sure what it means though...Does it means that the camera is tilted?

30 minutes ago, alacant said:

Hi

The coma is the same in all 4 corners. I don't think the reducer is gonna cover aps-c. How is it at f10?

My only (not too good to say the least!) experience with this type of telescope was with an orange coloured c8 and the 0.63 reducer. Without the reducer, it was ok but we still needed a refractor field flattener to get anything like.

JTOL but HTH.

Well I imaged only once on F10, but it was very bad due to many reasons, so I can't really say anything about that right now.

Also, according to the reducer in celestron's site: "Optimized for APS-C sized sensors, including most DSLR cameras and Nightscape CCD cameras" 

11 minutes ago, iapa said:

Try here: https://www.cloudynights.com/topic/600764-analyzing-field-flatness-tilt-etc-with-ccd-inspector/

 

 

Seems like the CCD inspector costs money though?

8 minutes ago, iapa said:

TBH my eyesight is not up to seeing your coma, I just see some slight stretch in top right

could it be camera tilt?

This is the right bottom side of the image for example:

I think the coma is quite visible, might not be completely horrible, but it is something I should really love to resolve.

As for camera tilt, not really sure tbh...Any way to check that? I don't see any reason for the camera to tilt.

3 minutes ago, TerryMcK said:

I can see the coma. It is very apparent. I'm not familiar with the scope so cannot really make any suggestions but no doubt there are other here who can.

Thanks for the comment

Hi, I bought a C8 Edge HD and been imaging with that for the past few months, I'm imaging with full focal length/reducer/hyperstar, but I'll refer to using reducer in this thread.

I'm trying to understand if my issue is backfocus issues, colimation issues, or maybe both or something else.
Here is a recent image I took of M16:

This is only the stack after ABE, as you can see there is coma, the C8 Edge HD should be pretty much flat field edge to edge as far as I'm aware.

I know that the required backfocus for the 0.7x reducer is 105mm, my backfocus was 105.1mm, which in F7 should be fine I believe.

I also worked for really long time on the collimation and thought it was very well collimated. Still, I'm getting this coma and not really sure why.
Would love to hear some thoughts about how that can be improved and what I could check.

Thanks for the help!