Return of the Double Stack - 21st June

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marktownley
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Return of the Double Stack - 21st June

Post by marktownley » Thu Jun 21, 2018 11:12 am

Hi All,

Long time no sun, busy at work and when have had free time been busy with other things... Anyways, if you remember my frustrations with inconsistencies I was having with my Lunt50 scope viewtopic.php?f=4&t=24369 well, I decided to go with Valerys suggestion of double stacked front mounted etalons, as, I already had one 50mm etalon (from the Lunt50) so decided to buy another with a view to double stacking them. Throw in a wait for various adaptors to be made and being busy at work and this morning allowed me to have first light. I mounted these on my 60mm f6 scope and used a BF15 as in the pic below.
Imageimage by Mark Townley, on Flickr

A smile came to me when I looked through the eyepiece for my first light, a lovely contrasty view!

ImageHa-Full-Disk-bw by Mark Townley, on Flickr

ImageHa-Full-Disk-colour by Mark Townley, on Flickr

For a first light i'm very pleased - the two etalons are not clocked yet, and the ERF on the inner etalon has not been removed yet, so, I know from experience there is still plenty of potential to improve the image further, I also have too much tilt on the camera (left of the disk is soft). What I like about this setup is that I can be imaging within minutes of being outside, which, for observing before work or in cloud gaps is important. Weather is supposed to be better for a week or so now, and work is quieter, so i'm hoping to do further tests. PGR chameleon 3 was used.

I hope i'm on a winner with this setup.

Mark
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Re: Return of the Double Stack - 21st June

Post by ffellah » Thu Jun 21, 2018 11:16 am

Very nice set up and beautiful results, Mark.

Franco

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Re: Return of the Double Stack - 21st June

Post by Montana » Thu Jun 21, 2018 11:20 am

Wow!! great images Mark :bow :hamster: I don't think you can beat a traditional etalon set up for great views down the eyepiece :)

Alexandra

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Re: Return of the Double Stack - 21st June

Post by krakatoa1883 » Thu Jun 21, 2018 12:50 pm

Very good contrst, the setup is really promising. Is that one your 60 mm apo ?
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Re: Return of the Double Stack - 21st June

Post by marktownley » Thu Jun 21, 2018 3:34 pm

Thanks everyone. Yup, it's the 60mm Tecnosky apo i'm using here Raf.
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Re: Return of the Double Stack - 21st June

Post by TheSkyBurner » Thu Jun 21, 2018 5:12 pm

Perfect solstice post!

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Re: Return of the Double Stack - 21st June

Post by Merlin66 » Fri Jun 22, 2018 12:01 am

Mark,
Looking promising!
As you know I used the SM60 double stacked external etalons on the ED80 for a while.....when they are "tuned" majic happens.
I'm sure you'll be successful.
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Re: Return of the Double Stack - 21st June

Post by TheSkyBurner » Fri Jun 22, 2018 3:49 am

I just noticed you are using a coronado blocking filter on the lunt system.

I had no idea they were compatible, do you notice a difference between the lunt blocking filter and the coronado blocker?

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Re: Return of the Double Stack - 21st June

Post by pedro » Fri Jun 22, 2018 10:57 am

It is surely a winner Mark. My experience with double stack front etalons is not great. I always have non uniform disks (lots of soft spots). Maybe I should try again

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Re: Return of the Double Stack - 21st June

Post by Carbon60 » Fri Jun 22, 2018 8:46 pm

Looking good there, Mark.

My 150mm and 250mm /Lunt 35 scopes utilise a Coronado BF 15. Works well.

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Re: Return of the Double Stack - 21st June

Post by marktownley » Sat Jun 23, 2018 8:29 am

Thanks everyone. I got a second adaptor that allows me to use the etalon setup on other scopes; here it is on my Skywatcher ED80, it also fits on the Tal100R too as there is only a few mm difference in the tube sizes.

Imageimage by Mark Townley, on Flickr
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Re: Return of the Double Stack - 21st June

Post by gabrieli » Sat Jun 23, 2018 10:42 am

Hi, Mark

I would be very happy if my full discs were that uniform, even after processing in PS.

I noticed that, in your first image, you have a Daystar Interference Eliminator. That's also my preferred method for handling Newton's rings.
I like how quick it is to find the minimal tilt you need and see the effect so quickly without fumbling with 3 pair of push/pull screws.

I do have a 2˚ wedge prism from Thorlabs in a c snout but, curiously, this snout, which was recommended by someone at Thorlabs, is not a 1.25" snout.
It's a bit less than that and isn't as secure as it should be. So, the wedge had to be secured in a proper sized snout.

When used with my Blackfly S, this wedge still leaves a small circular patch of Newton's rings on the right side of the image which I can't explain.

Lou

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Re: Return of the Double Stack - 21st June

Post by marktownley » Sat Jun 23, 2018 11:41 am

Thanks Lou, the interference eliminator is also my preferred method to get rid of newtons rings for exactly the reasons you state. This setup visually gives the most contrasty, if dimmer view.

Imageimage by Mark Townley, on Flickr

It will work well on days of excellent transparency to get nice big full disk mosaics.
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Re: Return of the Double Stack - 21st June

Post by eroel » Sat Jun 23, 2018 2:13 pm

Mark:
The FD´s are very uniform and contrasty.
Have a nice and sunny weekend,
Eric.

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