Solar Setup Advice

[astro_al]

I have been thinking about a white light solar setup for a while.

I observe using a binoviewer 100% of the time. Two out of my three scopes will work natively with my binoviewer and one requires at least a 1.7x glass path corrector. I use a Baader prism diagonal to preserve back focus and my binoviewer attaches via a Baader T2 quick changer bayonet. 

My plan is to purchase the Baader Herschel wedge along with the #27 adapter so I can screw the bayonet into the top of the wedge instead of the 2" click lock. Unfortunately the scope I would like to use the most is the one that already requires a glass path corrector (FC-76DC) and moving up from 1.7x to 2.6x is not going to offset the longer light path of the wedge.

Maybe I can do something like @Stu did:

If not then I will be using the FOA-60 with or without the extender as both configurations should have enough back focus when used with the 2.6X glass path corrector.

I like the idea of using the FOA in its Q configuration but am not 100% sure if the extender is OK to use for solar. I have seen one reference on Cloudy Nights to someone else doing this and a few more for the FS-60Q including @Rainmaker. I can always contact the manufacturer but first-hand experience is always good to have if anyone on SGL uses this setup.

Also, if anyone uses the Herschel wedge with the #27 adapter and a glass path corrector with the configuration where the GPC drops into the adapter (rather than screws into the binoviewer i.e. the Mark V) then I would be interested to hear that this works OK. From the Baader diagram it doesn't look like there would be enough clearance before the ND3.0 filter but it could be just me.

Finally, for those of you with the Baader Herschel wedge do you think getting the P version makes the most sense even though I will be using it for visual most of the time? The price of the P version with the extra filters isn't much higher than the V.

Thanks for reading.

Al

[astro_al]

To answer my own questions in case it helps someone else:

• FLO confirmed that the FOA-60Q should be fine with the Herschel wedge as the CQ optics are located well away from the focal plane.
• I ordered the P version as I think the 3 extra filters are worth the additional £40.
• There isn't enough clearance for a GPC when inserted directly into the #27 adapter, so the Baader diagram (below) appears to be misleading. I had a 10mm T2 extension tube so I added that to stop the GPC from hitting the ND3.0 filter. I should be able to swap the 10mm extension for a 5mm one if back focus turns out to be tight - no doubt it will be.

 

First impressions are that the Herschel wedge is a solid piece of kit. Removing the clicklock adapter was easy. Separating the ND3.0 filter from the 2" threaded ring was not. Once separated the filter's retaining ring needed tightening to stop the filter rattling.

A bonus is that I can use the removed 2" threaded ring to connect the wedge directly to the FS-152 without the need for a visual back (thanks to some other Baader adapters already used to couple the scope to a Baader prism diagonal). This should save precious back focus.

I now just need a clear day to see if the FOA-60Q and FS-152 will reach focus with the 2.6x GPC in place. I will probably try the FC-76 just in case but there is little to no hope it will reach focus unless my maths is bad.

Al

[astro_al]

The FOA-60Q reaches focus with 24mm to spare. That was with the M56 Baader clicklock and the 10mm spacer for the 2.6x GPC.

[astro_al]

After swapping the 10mm spacer for a 5mm one the GPC still appears to clear the ND3.0 filter. This, along with reverting to the original visual back, gives me 15mm more back focus to play with and is just enough (2-3mm spare) for me to use the 1.7x GPC which gives a more practical magnification range. Happy camper.

Edited February 11, 2020 by astro_al

[Paz]

Thanks for posting your notes, this will be very useful to others. Anyone using a wedge or binoviewers will appreciate the journey you have to go through to find enough in-focus!

[Stu]

Yes, it is all useful stuff. Just for fun as much as anything, I would like to use the Baader Wedge with my Telementor so will have to try to attach it directly to the T2 thread adaptor I have on the back of that which should allow me to reach focus.

[astro_al]

Update. I realised that with the #27 adapter I can screw three 2" filters into the wedge without contact with the prism. Adding in an empty filter cell above the ND3.0 and Continuum filters provides enough clearance for the GPC without the 5mm extension. 5mm saving is not a lot, but it means I can now use the FC-76DC with the wedge and 2.6x GPC with a whole 0.5mm to spare.