What can a Modder Expect?

[colinsk]

So, I have a fairly good understanding of etalons. I have a fairly good understanding of the surface of the sun and the doppler effect we can view. All of the commercial airspaced etalons that are internal do not cross the 50% aperture rule. If the aperture is 60mm the etalon is 30mm.

Why don't they make 100mm scope with 25mm etalons? If this was easy all the manufactures would be doing it.

So, to move an air spaced etalon back in the optical train we sacrifice field of view. When you are stitching images together this is not a problem. Or if you have specific active region to study visually it is a way to save money.

What benefits can a modder realistically expect? And at what cost?

[sullij1]

Colin,

Thanks for the informative rule summary. I will look forward to responses.

[marktownley]

You've summed it up nicely there Colin.

For me, one of the biggest reasons to mod is cost - A commercial solar telescope in the 100mm range is in excess of £5k over here in the UK and I just can't justify spending that much money on a scope. However a 100mm PST mod can be cobbled together all in for a shade over a quarter of this price.

Why don't commercial manufacturers make 100mm scopes with 25mm etalons - because, I expect, the shortfalls of a design like this - namely the whole of the fov is not on band. Now this is something i'm aware of, and as such never use my 'big guns' to try and do a full disk shot - only closeups. If I want a full disk I use my DS40.

[peter drew]

Also for me, cost was a significant factor, my 150mm F10 with internal 110mm D-ERF and BF15 set me back less than £1500. I've got used to the realatively small sweet spot and as the Ha detail changes whilst scrolling round, there is no need to retune. Added to this is the fun and satisfaction of engineering the mod.

[poita]

I guess the question is, has anyone had their 90mm PST mod side by side with a coronado solarmax 90 or a Lunt 80 and be able to tell us how much difference there is in the image for visual and for photography?

[colinsk]

That is the question!

[peter drew]

Perhaps not a direct comparison but I took a 6" F8 Skywatcher refractor PST stage2 mod with full aperture ERF operating at 125mm F10 to a popular large star party last year. It visually outperformed all 60mm and 90mm Coronado SS telescopes, the only downside was the small field of the 5mm BF in use at the time. The best view of all was with a high end APO fitted with two front mounted 90mm Coronado etalons, I guess this is what you pay the extra £££'s for.

[keithatrochdale]

A picture of one of Peters solar scopes, with the man himself for scale;

[keithatrochdale]

A detail shot of the 'stage 2' PST;

[marktownley]

A picture of one of Peters solar scopes, with the man himself for scale;



Well cool! B)

[Photonist]

Wow Peter, I’m ecstatic :woohoo:

I have in my garage a tube nearly this size, reserved for a future Istar lens. Have you posted some numbers or more info somewhere?

Regards,

Viljo

[peter drew]

Viljo.

The scope, mount and observatory are self built. The objective is a 220mm achromat F12.5. The main tube is 230mm OD made from two 8" Newtonian tubes. I have another scope built using a 150mm F10 Istar objective, the performance of which I'm very pleased with.

[colinsk]

Nice work Peter! Do you have any links to the design and construction of the observatory?

[peter drew]

Thanks Rusty, I can still learn a lot from you. :

Thanks Colin, I will try and generate another photo and a description. As for designs,I'm afraid they are all in my head or scribbled on bits of envelopes long lost!

[colinsk]

It must have been lots of bits of paper. :

[keithatrochdale]

Here you can see the outside of the observatory;




Here is Peter working on our Camera Obscurer, he also made the 28 feet dome;




He has a good head for heights;




Another observatory housing our 16" Meade;

[marktownley]

Absolutely fantastic 8)

Now, I just need to convince my wife we're going for a picnic in the Pennines one sunny day on a weekend :whistle:

[poita]

Truly amazing!

Though I am surprised that such a large scope is still using the black box!

Inspiring stuff.

[peter drew]

Poita.

The black box is empty, I machined the rear face to accept the BF15 diagonal.

[poita]

Excellent!

I attempted a similar thing, emptied out the box and attaching a 1.25" focuser on the back. I ended up replacing it with an SCT crayford focuser in the end.

I wish I was able to get out there and make use of the facilities, truly amazing setup. Makes me wish I hadn't lost my farm in the drought!

[keithatrochdale]

Absolutely fantastic 8)

Now, I just need to convince my wife we're going for a picnic in the Pennines one sunny day on a weekend :whistle:

Shall I put the kettle on?

[marktownley]

[quote]Absolutely fantastic 8)

Now, I just need to convince my wife we're going for a picnic in the Pennines one sunny day on a weekend :whistle:

Shall I put the kettle on?

not yet asked her, but a brew would be great when we do come up

[colinsk]

Mark, when you cross the pond I'll buy a few brews if I can pick you brain.