8 replies to this topic

[stargazer julie]

Sat, July 5 2025

 

Looked out, it was cloudy, then.... ta da, it cleared.  It's magic.

Lunt Telescope double stacked, in hydrogen alpha,
Imaged with Player One Saturn-M Camera (IMX 533) Using Sharpcap,  processed with Autostakkert, and Sharpened in Photoshop

 

[rigel123]

Looks good!

[stargazer julie]

Thanks.

 

It’s a challenge to get the tuning right on band by looking at my computer screen. I alternate between the eye piece and the camera, but the resolution of the computer screen and judging tuning on single images on the computer is something hard to gauge. 
 

Yesterday, I just could not get it quite right. 

[gstrumol]

Thanks.

 

It’s a challenge to get the tuning right on band by looking at my computer screen. I alternate between the eye piece and the camera, but the resolution of the computer screen and judging tuning on single images on the computer is something hard to gauge. 
 

Yesterday, I just could not get it quite right. 

You think that's tough? Try assessing the tuning while looking at the 3" diagonal viewscreen on the back of a DSLR (while under a blanket covering my head, the camera and the scope)! 

 

I feel your pain ... 

[rigel123]

Thanks.

 

It’s a challenge to get the tuning right on band by looking at my computer screen. I alternate between the eye piece and the camera, but the resolution of the computer screen and judging tuning on single images on the computer is something hard to gauge. 
 

Yesterday, I just could not get it quite right. 

I hear you!  And even when tuned with an eyepiece I typically have to tweak the tuning once I put the camera on.

[Foc]

When I tune my DS80mt often with a 1.6x barlow in place,it seems I have a single bed suzed sheet of decent tuning stretched on a double bed sized disc, easy to get the middle okay but one side or both tend to suffer.

Also the focal length for my 533mm camera and my Eyepiece ( without my glasses) are quite different and I feel that either tuning changes when I swap and change fl or I must have lazy eyes.

Edited by Foc, 05 July 2025 - 09:59 PM.

[stargazer julie]

When I tune my DS80mt often with a 1.6x barlow in place,it seems I have a single bed suzed sheet of decent tuning stretched on a double bed sized disc, easy to get the middle okay but one side or both tend to suffer.

Also the focal length for my 533mm camera and my Eyepiece ( without my glasses) are quite different and I feel that either tuning changes when I swap and change fl or I must have lazy eyes.

It's interesting that you say that the middle is on band while the edges are not.   I have a similar effect when I use the 60mm stack unit instead of the 50mm stack unit.  I can sometimes tweak the viewing area to get better tuning, but not always.  I think that the larger the aperture, the more difficult it is to get everything in tune.  It requires great optics right to the edges, for one, but I'm sure there are other effects since I can sometimes get good tuning with the 60mm stack unit, and other times, I cannot.

 

I don't think I have to retune when I swap the eyepiece for the camera, but I have to refocus.

[KWhitt]

Thanks.

 

It’s a challenge to get the tuning right on band by looking at my computer screen. I alternate between the eye piece and the camera, but the resolution of the computer screen and judging tuning on single images on the computer is something hard to gauge. 
 

Yesterday, I just could not get it quite right. 

 

I can tune my single-stack Lunt 60 decently from sharpcap by watching the number the sharpcap histogram shows.  I set the exposure so nothing is saturated, and then just adjust the pressure up and down until I'm at the minimum value on the histogram.  I have not been able to figure out a method for when I'm double-stacked.

 

I did some experiments the other day, with just the SS, with two goals:  1) see how accurate the above method actually is, and 2) see how small adjustments to the tuning knob impact the tuning.  I started with a visual tuning and focus.  Then I put the camera in and tightened the tuning knob until it was clearly off-band.  I took a 30-second video and noted the histogram %.  I loosened the tuning knob by two letters worth aligned to the top of the scope (or spaces or punctuation from "LUNT SOLAR . DOPPLER TRUE TUNING ."), and took another video and noted the %.  Continued this process until it passed through a good tuning and was off-band again.

 

Then I stacked all the videos and sat down to review the images and the data.  And realized I screwed up, because I didn't have the sun centered in the sweet spot (it was a little to one side), and because I didn't notice a cloud passed overhead, right during the 'best' tuning video.  I'll need to repeat this another day.

 

 

As far as tuning from the computer screen when a DS is added--I'm still thinking about how to come up with an experiment plan.  Since my DS is a tilt tune, that shouldn't need to change as the session goes on (let's assume an initial visual tuning was performed after at least 15 minutes of acclimation time), right?  I think my goal would be to see how the sensitivity of the pressure tuning compares when DS vs. SS.  Because my end goal is to be able to retune during a longer imaging session without having to swap to visual and back.

 

 

It's interesting that you say that the middle is on band while the edges are not.   I have a similar effect when I use the 60mm stack unit instead of the 50mm stack unit.  I can sometimes tweak the viewing area to get better tuning, but not always.  I think that the larger the aperture, the more difficult it is to get everything in tune.  It requires great optics right to the edges, for one, but I'm sure there are other effects since I can sometimes get good tuning with the 60mm stack unit, and other times, I cannot.

 

I don't think I have to retune when I swap the eyepiece for the camera, but I have to refocus.

I figured out I needed to start with the camera in place, set up so the sun is in the Jacquinot spot of the SS, and then swap back to visual for tuning (and don't adjust the viewing area again).  Finessing the placement in the Jacquinot spot is much easier by camera than by eye, at least for me.

 

Kristie
 

[NuovaApe]

There's certainly correlation between a good tune and its histogram.

Douglas Smith over on SolarChat posted a sequence of SHG images with varying tune.

I took the liberty of loading them into GIMP and displaying a histogram for each one.

 

This is an animated GIF. You might need to click it to play it.

 

 

The on-band image is in the middle - row 2 column 3.

 

Ed.