DS-ing Lunt LS50 and Quark

[krakatoa1883]

My first experiment of stacking Lunt LS50 and Quark Chromosphere. I used my Quark without its telecentric (a very poor one in my unit) replacing it with a Baader VIP on the nose of the diagonal that results in about 4x at the etalon distance and minimize the CWL shift. This time I removed the Lunt diagonal for making use of the Quark BF, next time I'll try to make use of the Lunt BF to see if something change (any suggestion ?).

ds3.jpg (282.32 KiB) Viewed 1333 times

Below is the only image of today in DS mode, seeing was bad this time however the result seems promising. I have still to find the best setup, tuning both Quark and Lunt up to the best combination (again, thanks in advance for any suggestion).

AR12687 H LS50 b.jpg (37.02 KiB) Viewed 1333 times

Unfortunately the setup requires a Barlow lens or a focal extender because the Lunt LS50 has a very short backfocus, it is therefore impossible to image the whole Sun in DS unless assembling a mosaic which I am not willing to do, or using a very large camera sensor. The disc below has been made without Quark.

H alpha fd.jpg (44.48 KiB) Viewed 1333 times

[eroel]

Raffaello:
Good image in DS mode and nice FD.
Regards,
Eric.

[marktownley]

Nice pics! Whats a Baader VIP?

I don't think you're narrowing the bandpass like a true double stack as there's still the double limb visible, and this continuum leakage goes when units are working properly as a DS.

[krakatoa1883]

Thanks Eric and Mark.

Mark, you're right, I noticed that with this setup contrast increases compared with the LS50 or Quark alone, but it still not a true DS, the double limb is in fact still there. As the next step I am replacing the VIP with a Powermate and searching a better tuning for both devices. I don't expect much progress but I think that there can be some margin for improvement.

Would a Lunt DS module eliminate the double limb ? I am planning to purchase one but I would like to be sure it's worth it.

[bart1805]

Hi Raf,
I think you should be able to get rid of the double limb effect with the Quark and the Lunt etalon. My suggestion would be:
Tune the LS50 and the Quark independently to get the best view for both the single stacks. Than combine them. And try fine-tuning just the LS50 to see what the results will be.
Good luck! Bart.

[marktownley]

The Baader VIP is just a barlow, you need a telecentric beam for the quark to work.

You won't get a double limb with the LS50 double stacked with an external etalon, here's a pic I took last weekend with mine double stacked this way

ha-full-disk-bw by Mark Townley, on Flickr

[krakatoa1883]

Thanks Bart & Mark. I spent all afternoon making further experiments but I couldn't get nothing better than the above image, even worse if my Quark is used with its native telecentric. In fact an ordinary Barlow - if placed as far as possible from the etalon, provides more contrast and less diffused light, and this remains a mistery to me.

Thanks for your advices.