spectro-aras.com

To: Group,

I've finally got a replacement Cmos camera for use on the eShel; saving the FF Zwo ASI6200mm for other astro imaging.
I'm using a Zwo ASI2600mm cmos camera and have roughly focused it with the 135mm Canon camera at F/2 ontop of the
Shelyak eShel. Here is an image from the camera using the Th-Ar light source:


I was wondering is I should proceed further seeing that the right-side of the frame has such badly trailed Th-Ar light on
these orders. Tilting the plate (either btw the lens & the eShel or btw the camera & lens) has negligible effect on
getting the right-side of the field looking better. I remember when I did this 2-3 yrs ago, the totality of the image had
much better Th-Ar points, and I was able to successfully process a Vega spectrum; see:


Unfortunately, I had to tear everything down moving 120 miles north-west of LA so I'm essentially starting over. One thing I'm doing now, is that the Canon 135mm is set for F/2. Previously (2-3 yrs ago) the 135mm lens was set at a larger (>f/3) focal speed. Any suggestion would be helpful.

James

James,

I would like to help with your problem but I'm not able to see the images you attached to your post.
Not sure if this is a problem at my end or at the forum.

Bernard

At Shelyak, we've tested a wide range of lenses, and only the 135mm Samyang lens gives good results.

Here's a picture of a thorium/argon lamp with an ASI 2600 and a 135mm lens



You also need to ensure the right back focus between camera and lens (depending on the camera used). Here are the rings to use depending on the camera.



We're currently working on a dedicated non-photographic optic that will be much better in the blue end of the spectrum.

To: Olivier,

Thanks for the images! Yes I'm not using the spacer but will try that out.

To: Bernard,

Do not understand why you cant see my images.....I can see them on this forum even when not logged-in.

Thanks for all the feedback!

James

James,

I can't see your images either. Using google chrome browser on windows 10. Also not possible with Android smartphone. Only the icons of both images are visible. Login into the Aras forum makes no differece.
Best regards
Hugo

Hi James,

I tried with the Firefox browser and it works! (Sorry, not your problem)

Best regards
Hugo

To: Hugo,

Yes I used my IP to upload these images in firefox.

James

To: Olivier,

RE:"At Shelyak, we've tested a wide range of lenses, and only the 135mm Samyang lens gives good results."

According to the Christian's write-up, the Samyang lens only work to about 4000A; anything shorter is absorbed...plastic
internal lens? He uses the excellent (but no longer manufactured) Canon 135mm F/2 L-lens

RE:"Here's a picture of a thorium/argon lamp with an ASI 2600 and a 135mm lens"
The picture on the right with the 135mm lens is a Canon 135mm F/2 L-lens (red rimmed marking gives it away)
Lucky I purchased this lens 3-years ago for this project.

I used the 16.5mm extension and while the stars are better, I may need to tweak the tilt to get best results.
I have this tilt in my notes when I had it set-up in LA, but I'm using a new camera and needed to get rid of the 1st-order effects,
focus-spacing, before I tackled the 2nd order, tilt. Thanks for the great feedback....hope to get a Vega spectrum before
it sinks too far west.

James

Hugo wrote: Fri Nov 29, 2024 12:27 pm James,

I can't see your images either.

I have seen this kind of problem before. I think it is a browser security setting that prevents displaying images hosted elsewhere on a non secure (ie not https) site. For example this is the address of one of the images
http://astroimage.info/files/Vega_thor_bin-2.jpg
Can you see the image if you click on this? If so try right clicking where the blank space where the image is and go to the image address direct

Cheers
Robin

Hi Robin,

You are right. Thanks!
Right click on the image icons of James in Windows Google Chrome browser or push and hold on Andoid, results in a drop down menu from which I can select to display the images.
Back now to the real topic: the echellograms for calibration.
Best regards
Hugo