First light Stellarvue 127 + LS50 etalon mod

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gabrieli
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First light Stellarvue 127 + LS50 etalon mod

Post by gabrieli »

A while ago I read in a post that the back focus required for the LS50 collimating lens was 180mm, I measured the distance to the focus point on my Stellarvue 127 and found it was about 200mm (from end of draw tube. I removed a detachable 60 mm section of the scope to give myself more leeway.
I marked the collimator position and attached the etalon module and found it very easy to achieve the right back focus distance. This was not possible with my AR152 without cutting into the tube. I had no concerns about the weight of the module since it is fairly compact, with a solid feel, and light.

Setup used for images below
setup.png
setup.png (597.29 KiB) Viewed 306 times
module.png
module.png (1.08 MiB) Viewed 306 times
I used an ASI1600 to record files and found that this setup won’t give good full frame (4600x3500) view but will produce workable results when the ROI is reduced to 2400x1900 or less. Physically, this reduced ROI
Is the size of a 2/3” sensor.

this image was not processed (except for wavelets)
lo wide.png
lo wide.png (507.17 KiB) Viewed 306 times
this image was processed with wavelets and levels for contrast
hi filament.png
hi filament.png (859.49 KiB) Viewed 306 times
I used a B600 for this session but I’ll try other blockers next time.

I already have all the adapters for assembling a module with an LS60MT etalon (all repurposed PST connectors and M48 extension tubes for the nosepiece) but I have some concerns about the weight of the LS60MT module.
It does feel solid but the nosepiece connects to M50 threads that connect directly to the inner etalon housing unlike the nosepiece for the LS50 module which connects by way of an M68/M48 adapter to the outer housing of the etalon with large M68 threads. I’ll try it and if the LS60 module gives a more uniform image, I may go that route too.

In the meantime, I'll keep my eyes open for any information or advice I see in other peoples' posts about simlar setups.

Lou


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Re: First light Stellarvue 127 + LS50 etalon mod

Post by Montana »

That's a great first light Lou :bow :hamster:

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Re: First light Stellarvue 127 + LS50 etalon mod

Post by MAURITS »

Great description and images Lou.


Regards,
Maurits

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Re: First light Stellarvue 127 + LS50 etalon mod

Post by marktownley »

Good first light Lou!

Don't forget there will be a sweet spot associated with a setup like this so you will need to ROI accordingly.


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Re: First light Stellarvue 127 + LS50 etalon mod

Post by MichaelTeoh »

Is it possible to use a LS152 module on a 228mm refractor?


Michael Teoh, Penang, Malaysia
APM-TMB 228/2050, Lunt LS152
https://www.flickr.com/photos/michael_teoh
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Re: First light Stellarvue 127 + LS50 etalon mod

Post by gabrieli »

Hi, Michael

I have an LS152 which I double stack with a Quark Chromosphere and it gives great results. I just have to add a 5 inch extension tube before I attach the Quark.

If you are going to use your LS152 module, you will have to find out how far in from the 228's focus point you need to place the module so that its first collimating lens is at that special point (back focus distance). You would have to first find the focus point of the LS152 without its Ha module attached and see how far in from this point the first collimating lens is located when the Ha module is attached. This distance would be the back focus distance for the 228.Then, assuming you have the required adapters, the setup should work.

You can also ask the question on this forum and see if anyone knows this distance. I've never had any reason to do this measurement although it should be easy enough.

Ihope this works for you.

Lou


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Re: First light Stellarvue 127 + LS50 etalon mod

Post by Rusted »

Lou,

Thanks for sharing your mods. :bow

You raise an interesting point about the attachment of the larger and heavier Lunt 60mm PT etalon.
I thought I was being clever in ordering an inexpensive, Omegon 2" eyepiece/focuser extension x 35mm long.

If I skim 0.5mm off the bore of the extension, in my lathe, then it will fit the filter/nosepiece of the 60mm Lunt etalon.
2" push fit is 50.8mm. The nose of the Lunt 60mm etalon is 51.8mm in diameter. The difference is only 1mm.
I don't think such a small difference will affect the bronze clamping ring.
The 2" nosepiece of the adapter is threaded for 2" filters and/or further extensions.
These will fit inside the standard 2" focuser clamp.

The downside, compared to Marty's 60mm mod, is the slight increase in mechanical length of my attachment method.
The RAF adapters Marty mentions are not readily available in Europe. As far as I know.
T-S want three times the price for their similar adapters + their ridiculous postal charges.

Here is the sort of extension I am talking about. Only it is the longer 50mm version. I have the shorter 35mm on order.
This will clamp onto the filter/nosepiece of the Lunt PT 60mm etalon.
Which is fitted with quite a long thread. Suggesting, to me, adequate strength in this size for supporting just a ZWO camera.
Though not ideal for a double stack set-up. Nor a Quark addition nor a DSLR.

P1040676 rsz.jpg
P1040676 rsz.jpg (118.25 KiB) Viewed 232 times


http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: First light Stellarvue 127 + LS50 etalon mod

Post by MichaelTeoh »

Hi Lou, thanks for the info. I am a noob in terms of equipment, gotta figure out the calculations.

Anyway, I believe an ERF will be required for such setup. Can't afford that for now. So, just keep this idea for the future.

Cheers.


Michael Teoh, Penang, Malaysia
APM-TMB 228/2050, Lunt LS152
https://www.flickr.com/photos/michael_teoh
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