Rusted

So that's what what the spot was supposed to look like? Nice capture! The teasing sun had me all set up after lunch. The seeing was such mush I couldn't focus properly. Then SharpCap said my storage was full. So I deleted 200Gb of old captures. By which time the sky was solid, grey concrete. "Get a nice retirement hobby," they said. "Go over to the Light Side." "Sunbathe, while you capture living images of the sun." Yeah, right! 🤣

A 3" f/10 should show very little false colour. It is almost equivalent to a 4" at f/15. Poor seeing conditions often lead to increased visibility of chromatic aberration. Low altitude objects similarly. A combination of both do not lead to eternal joy.

Spherical aberration is colour/wavelength independent. Optical surface roughness is also colour independent. iStar offer h-alpha specific achromats. World class solar imagers use iStar H-a objectives. I find my 150/10 iStar H-alpha objective a real improvement over my Celestron 150/8. Even with a 1.125x GPC, to produce f/10, the Celestron was inferior in H-alpha to the iStar. Larger H-alpha refractors tend to be used at high magnifications. Both for imaging and visual. Putting high demands on optical quality in the entire optical train. An APO may have poor correction in the deep red. The iStar H-alpha objective provides high quality mono images of the sun in white light with a wedge. Its close-up moon images are also of very high quality when the seeing allows. This is just another option. Rather than modifying a premium APO. Where originality is highly valued. You will still need one [or two] H-alpha etalons, a D-ERF and blocking filters. Plus a sturdy mounting to handle the long and heavy instrument.

You can use fuel hose or rubber hose as a "universal joint" in a shaft drive. The problem is finding a small enough [hose?] clamp for each end.

The flexible joint is probably a standard item if you poke google with a sharp enough stick. Try something like: skywatcher flexible motor drive joint. 21 Euros + similar freight charge from a famous German dealer. Get one free with every skywatcher DC drive motor purchase.

I use a Baader full aperture D-ERF on my 150/10. Yesterday I was using some black, camping mattress foam, to measure where the focus was sharpest. It is much easier to see the sun's disk on smooth, black material. Rather than blindingly bright [or red] on white. Without the usual "protective" IR/UV blocking filters smoke soon rose from the foam! The burn left a shiny trail on the foam surface. So much for the Baader D-ERF having a cool beam! I now use an additional Baader 35nm H-alpha, 2" filter. Plus a Beloptik KG3. Both are stacked in front of the PST etalon. These really do ensure a cool beam after the D-ERF. I had the same problem with a burning beam with a 90mm Baader sub aperture D-ERF inside a 150/8. That mistake cost me a ZWO camera. I would never trust a Baader D-ERF alone to protect a 150mm H-a system. Try it for yourself. You can instantly burn your hand, or your clothes at focus after a D-ERF. When it is the only means of protection from a 150mm objective. I have shiny burns on my black, down jacket. Where the beam accidentally shone on it during adjustment. It is easy to forget when your are checking focus without the usual optical train. You glance down to see smoke rising from your clothing! Let's be careful out there!

An excellent set of images.

Try repeatedly clicking on the image. The first set is tiny but then I get large disks.

Lots of nice, crisp detail all over the disk. Excellent scale too. Well done! It reminds us that there is a great deal of activity away from the most "photogenic" spots.

Overcast for most of the day. Cleared around 16.00 to thin, high cloud. Best so far.

Thanks. I saw Chainsaw Massacre.

Thanks. My wife saw a rabbit.

Lovely, warm, autumn day but lots of cloud and high haze. 912x912. 1.6x GPC. Resized to 700 pixels from 800.

F/30 on my 150mm? Not likely! It would put impossible demands on my typical seeing conditions. I can't even add a 2x 'Shorty' Barlow to my PST mod. Have to make do with 'wimpy' GPCs on the nose of my '174.

Not the most transparent of conditions + thermal agitation + wind blowing the scopes around.

You're doing great! The detail is excellent! So I don't want to sound the least bit critical. Gentle advice is what I offer. I have been very grateful for those who helped to shorten my learning curve by several years. I'd use longer exposures to get your Gain right down. Around 10ms should avoid needing so much gain without harming your results. I usually capture at 10ms and only reduce the exposure if the Gain is well below 100. Captured as AVI 8bit mono in SharpCap. I routinely select 75 frames out of 500 in Autostakkert AS!3.14. This was recommended to me here and I found it works well for me. I have tried up to 3000 frames but it doesn't add anything. Others will disagree. I then move on to the truly magical ImPPG for finding the amazing detail hidden in the still image after stacking. ImPPG needs a very gentle touch. It can cause hair loss and sleepless nights. Ease off on the post processing. Less is more. Avoid over-sharpening. This is easily recognizable as an all over, granular effect. Zooming in slightly will show this more clearly. Try to keep it natural looking and "real." The ZWOASI174MM camera is popular. As are other cameras with the same sensor. Camera choice depends on the pixel size suiting your telescope's focal length. Under-sampling and oversampling are the terms for tonight's homework. Then you can tell us what it all means.

Excellent! It probably needs a handle for easy management in transit. BTW: Does it work?

I have hacked cigar lighter plugs off other kit when I was desperate. There's nowt wrong with mini-jacks.

I have had similar problems. Desperately trying to find where AS!3 has hidden its output. Sometimes [rarely] it unexpectedly sharpens when none is ever requested. Just opening the file in ImPPG shows the AS!3 output file is worthless. Operator error? It usually is in my case. All that said, it is a brilliant piece of FREE software and we wouldn't want to be without it.

Owning or having access to a printer is not remotely the same thing as having the skills and capacity to stretch its limits to such astonishing levels. Very few would have the imagination and such a unique understanding of the 3D geometry and vital requirements for designing and completing such a project. This is no small feat. Even after a lifetime of seeing what individuals can accomplish I am deeply impressed.

Blimey! Does Elon know you've borrowed his alien technology?

Define "trashy."

Excellent Steve.

Fascinating. The flare was in a different position compared to yesterday's H-alpha flares.

Thanks. Probably just better seeing conditions. I seriously doubt your AOK Swiss adapter can be the cause. My own PST etalon can be very frustrating in its on-band, sweet spot repeatability. I believe it is down to rotation relative to my Lunt B1200S2 blocking filter and tilt. I am presently "clocking" the B1200 "nameplate dimple" to match the focuser orientation. The etalon doesn't rotate relative to the focuser. So the focuser is an easier target. Note that I am using a rubber band to pull the etalon into a tilt. I have a rod screwed into the etalon inner circle. The rubber band pulls on that. I rotate to tune the etalon and simultaneously tilt to darken the frame evenly. The rubber band just maintains the tilt. Though it is still quite a fiddle. I ought to make an etalon tilter plate but I am too busy at the moment. I also have a Baader 1.25x binoviewer GPC right behind the etalon to spread the sweet spot. The etalon holds the GPC in the AOK Swiss baffle. Which I had to open out a tiny bit in the lathe. Almost no change in baffle opening. So it could be filed or sandpapered. Wrap the paper around a suitable bit of dowel to make a smooth aperture. Do not open up the AOK Swiss, rear adapter without remembering the GPC or it will fall right out!