Problem getting my SV60 SolarScope to focus when trying to image

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mikepaling
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Problem getting my SV60 SolarScope to focus when trying to image

Post by mikepaling » Sun Jul 23, 2017 1:19 pm

Hi Folks .... I hope that I am in the correct forum section with my question.

I purchased my SV-60 SolarScope direct from Ken Huggett in may last year .... it works great visually.
I have recently been trying to take images of the Sun with no success at all :-(

I am having mega trouble getting my DMK mono CCD camera to focus correctly. For several weeks I have been trying to set up a "straight through" optical path (ie: not using a diagonal) and have been using all sorts of extension tubes ( I have a lot of them!) to get the correct back focus distance without any success at all.

Does anybody out there have any experience of making images through a SolarScope successfully?
After removing all removable parts from my SV-60 .... does anybody know the distance from the back end of the scope to the sensor on my DMK camera???
Any help & suggestions would be very much appreciated

Mike

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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by marktownley » Mon Jul 24, 2017 6:51 am

Hiya Mike.

You do have the blocking filter in place when you are trying to image?

Mark
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Montana
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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by Montana » Mon Jul 24, 2017 7:19 am

I have a Solarscope but a detachable etalon (not an all in one scope). I am also thinking the same as Mark, you must keep the blocking filter in?
Do you have some photos so we can see?

Alexandra

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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by Montana » Mon Jul 24, 2017 8:38 am

There also seems to be an extension tube to give the SV60 a f8 ratio, you have that in place too?

"The additional tube length required for the SV-60 to achieve f/8 is provided by an extension piece which assembles onto the main tube body. This quick and easy to assemble extension, allows the SV-60 to be carried around in the same size carry case as the SV-50 while retaining its greater image scale." http://solarscope.co.uk/sv-range.html

Alexandra

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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by mikepaling » Mon Jul 24, 2017 4:59 pm

Hi Alexandra and Mark .... thanks for your thoughts .... but ....

The rear blocking filter and the "additional tube" at the front end of the scope are both in place when I am trying to get the SV60 to focus.
I have basically only removed the diagonal, that I use for visual use, from the SV60 and have been adding all sorts of combinations of extension tube to try to find the correct back focus position for my DMK camera.
The focussing tube on the SV60 does not have a big range of movement, in or outwards .... unlike my 3.5" feather-touch focuser that I have on my main APM refractor.
I know that the SV60 can be used for solar imaging .... I have seen sooo many images that people have put onto the internet .... but I just can't seem to make any progress with my SV60 :-(((

Mike

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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by Montana » Mon Jul 24, 2017 5:44 pm

Have you tried imaging with the diagonal in? I am sure it will be fine as the optics will be really good if it was provided with the Solarscope, Ken is very fussy about the optics he chooses :)

With my TEC140 if I use a diagonal for focus, then I need about 10-15cm of extension tubes if I remove it, I don't know if this is relative or not to other telescopes?

Alexandra

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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by Bob Yoesle » Mon Jul 24, 2017 6:28 pm

Hi Mike,

Assuming you don't have an in-travel issue, it should be a simple matter to locate the CCD sensor at the appropriate focal distance, which you can measure within a couple of mm of accuracy without the BF in place. Use a white card and measuring stick, and place the white card along the stick, moving it until you get a focused image of the red H alpha solar disc. Then use the appropriate extensions to put the camera sensor at that distance (using the blocking filter of course).

However, there is the possibility that you may have another problem. The SolarScope ERF's have some near IR throughput above 700 nm, and the blocking filter might be leaking some near IR etalon peaks:

Solarscope-ERF-lin.gif
Solarscope-ERF-lin.gif (138.2 KiB) Viewed 1103 times
This IR will be seen by the camera (but not your eye) and may appear as out-of-focus continuum, depending on your objective's ability to focus IR concurrent with the H alpha line peak. Any out-of-focus IR will make it difficult to focus:
DSF 100 DSBF 182012 rotate crop.jpg
DSF 100 DSBF 182012 rotate crop.jpg (195.24 KiB) Viewed 1103 times
Luckily, this near IR leakage is easy to remove -- Near IR leakage (note out-of-focus sunspots and solar limb), top; with added Baader R CCD filter, bottom:
IR leak.jpg
IR leak.jpg (218.44 KiB) Viewed 1103 times

Try a simple IR blocking filter to eliminate this possibility. The Baader UV/IR filter, or Red CCD filter work well for this:
baader-r-ccd-filter-1-1-4--ca8.jpg
baader-r-ccd-filter-1-1-4--ca8.jpg (179.59 KiB) Viewed 1103 times
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mikepaling
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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by mikepaling » Mon Jul 24, 2017 7:44 pm

Hi Bob ...
This looks interesting ... I will investigate when I obtain some of these filters ... and .... when the Sun decides to show itself!!!

Regards Mike

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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by Montana » Tue Jul 25, 2017 7:00 am

I was coming to that Bob :) I wanted to see if he could focus with the diagonal as it should be the same as by eye. If he could see by eye but not with a straight swap with the DMK then it would be the problem you stated above. We were getting there :) :) :)

Alexandra

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Re: Problem getting my SV60 SolarScope to focus when trying to image

Post by Bob Yoesle » Thu Jul 27, 2017 7:32 pm

Hi Alexandra,

Great minds think alike don't they ;-)

Just hope it's a true focusing issue and not a leakage issue (even though it's a simple fix), and that either way Mike can get things sorted out...

Best wishes,

Bob
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