Rusted

Hi Stu, I just had a look in white light. At least four dark spots in my old Vixen 90mm/f11 with Lunt wedge. The sun has come back out again after loads of cloud but the seeing has gone completely mushy in H-a.

A sunny morning had me back in the observatory. Nothing worked! Flat batteries and Firefox madness. I managed a couple of poor captures through clouds but nothing since.

I saw a complete chain of Starlink satellites crossing the sky one night. Even after sixty years of amateur astronomy it was completely surreal! They too disappeared into the Earth's shadow. It is rare not to see some satellites when you enjoy dark skies. May I recommend a pair of binoculars to allow you to see more? 8x40 is a nice size. Light to hold and carry and can be used to admire the sky, the view, birds and animals. The modest magnification avoids exaggerating any handshake and makes finding stuff much easier. Keep looking up and be safe.

Nice! Ideally, you should weigh both [complete] OTAs and then space them away from the DEC axis. To balance their moments just like a simple see-saw calculation. Mass x distance from the axis. I used a crossbar on either end of the saddle. Then placed the heaviest 180mm OTA closest to the DEC axis. The lighter 150mm was then spaced on the other side of the DEC axis spaced to balance the pair. It worked. With three smaller OTAs you'd weigh all three. Place the heaviest in the middle of your two crossbars. Then add the balanced OTAs. Carefully spaced on either side according to their calculated moments.

I should have said more clearly that the balance problem is applied torsion around the DEC axis. Some people add a weight on a stalk at right angles to the saddle and DEC axis. I tried that but ended up calculating the moment of the OTAs around the Dec axis as if it were a simple see-saw.

I have hung three refractors 180/150/90mm from my big DIY GEM but it needed very careful balancing. Get it wrong and you introduce serious asymmetric imbalance [torque] with different sky pointing positions. I'm not talking about simple balance around the Polar Axis or even the DEC axis. Though that needs to be correct. I "wrap" my OTAs around the cradle to avoid adding too much moment. Main OTA flat on the saddle. The other two each side of the saddle. Fortunately I have a channel shaped saddle. You could try getting a suitable bit of channel to fit on your saddle if the idea appeals. Worst case scenario is a series of OTAs stacked "in series" away from the saddle. Each OTA supporting the next. It also loads the first OTA's tube rings because they must support all the other OTAs. The Cog G of each complete OTA/camera/at focus ought to be individually balanced by sliding them through the tube rings. Remember to tighten the rings afterwards. You'll need extra counterweights to balance the heavy load. When you get close to balance you need complete freedom of the axes as you try pointing all over the sky. The clutches can easily spoil the balance until it suddenly lies beyond a critical point. I like to give the OTAs a very gentle shove as this is much more sensitive than static balance. You can better sense any bias in one direction. Keep a tight hold on the set-up or you might get a rapid nosedive! I doubt you'll need the restraining ropes I use to avoid disaster.

One rural neighbour had 19 insecurity lights at the last count. The next along has his very own "Close Encounters landing strip." Another left the carport lights on three years ago and still they remain on. So I took up "solar" and no longer care about local light pollution.

Slightly off-topic but the absence of aircraft must be worthy of some unique research into other side effects. Atmospheric, cloud formation, albedo, jet stream, bird migration and song and behaviour, where noise is a factor? We see fewer trails per month now than we did in an hour pre-2020. Always high altitude back then and usually without audible sound thank goodness. Persistent trail conditions would have the sky liberally criss-crossed. It was interesting to see aircraft cross the sun. Leaving thermally agitated trails, drifting away.

Very nice. Even better as a JPEG. So everyone can instantly admire your skill.

Well done Nigella! It looks as if NASA will be envious as soon as you get some favourable seeing.

Get cracking! There is no absolutely excuse for recalcitrance with a shiny new camera! Especially a shiny new ASI1600 bright red Roundtoit! Get a fast imaging laptop with SSDs and lots of USB3 ports and you won't regret it. I used Samsung T5 external SSDs on my ASUS N552V imaging laptop on USB3 cables and ports. They were always a nuisance dangling off the imaging desk and using up ports. I was constantly clearing them of videos at short intervals to make room for more. So I replaced the only [tiny] 256Gb SSD internal drive with a pair of internal 1TB SSDs: Samsung 860 & 970. Speed increased noticeably over the 1TB T5 external SSD and startup time considerably shortened. The ASUS has a hi-res screen when open, but drives my 27" Hi-res AOC imaging monitor for my observatory. Seeing such a huge, live, image of the sun in H-a is a great aid to finding and imaging interesting detail and proms. I use the ASI174MM with my long focal lengths on my PST mod refractor. 150mm F/10 x various GPCs for even more scale. Solar imaging literally took over my life and I practically live in the dome whenever it is sunny. Lots of imaging time means lots of practice getting it right. Plus lots more chances for better seeing. Lots of active time means the costs per week, day, hour or minute actually begin to make sense. If only to yourself.

Many thanks for a brilliant idea! That's a very clever, alternative method. It also provides for an easy reach when cutting out the slit from the inside. Access to the outside of the dome has proved incredibly difficult. Even with the dome resting on levelling blocks on the ground. It never occurred to me to work from the inside. Thanks again.

The problem: Draw two, straight, parallel lines, one metre apart, on a hemispherical [domed] surface for cutting out the observation slit. "There are no parallel lines in spherical geometry. Only great circles." So sayeth iTinerant. If you draw parallel lines on a dome to mark the observation slit then they will looked oddly curved. You can't just use a steel rule or wooden ruler. You can't stretch cord or tape between the start and finish points. If tensioned, string and tape will always adopt great circles. You can't assume lines a given distance apart are straight. Though they might well be parallel. Like railway lines. If you try to measure the spacing between your two lines then a metal tape measure can't bend around the curve. A cloth tape measure will do, but would measure a longer curve. Rather than the desired [straight] chord between the lines. I see two possible options: Plan A. Find the exact centre of the top of the dome by measuring up from the skirt. Using a fibreglass surveying tape from multiple positions around the skirt. Mark the top. Project a vertical [laser] line, centrally onto the dome to coincide with the marked top. Then draw the projected line onto the dome down to the skirt. Measure out 50cm from this central line to form parallel lines one meter apart. Placing the laser head too low and the beam never reaches the top of the hemisphere. If the dome skirt isn't perfectly level then accuracy flies out of the observation slit. Fortunately that can be checked too. Using the 360° horizontal line also provided by the "universal" laser. Plan B. Project "parallel" lines on the dome from two, raised positions one meter part. Draw these lines on the dome prior to cutting out the observation slit. Plan C. Complete both plan A and B to check each other's result. Are any of of my plans a sound procedure to ensure accuracy? What haven't I considered? How would you go about drawing these "parallel" lines? Thanks.

It has almost all been covered by previous posters. Like Peter, I am only interested in "close-ups." Except that I image. I used a very secondhand 6" f/8, internal 90mm D-ERF, PST etalon, original blocking filter and ASI120MC camera for a couple of years. Having had more fun, more often, than in all of 5 decades of the dark side, it was time to invest more heavily. Now I use a 180mm Baader D-ERF, iStar 6" f/10 H-alpha objective, PST etalon, Lunt BF1200S, FT2535 focuser and ASI174MM camera. I had to make my own main tube but everything else is just screwed together from standard parts. Since I practically live in my DIY 10' domed observatory during sunny days, the cost per minute has dropped like a stone. As already mentioned: You need good seeing for close-up images. Early morning or late afternoon are usually best. Though there is always a chance of lucky seeing. Your choice of H-a filter will decide the required focal ratio of the donor telescope. An off-the-shelf H-a scope will have made the choice for you. Buy from a reputable dealer. Or test a secondhand instrument yourself. Just because a seller belongs to a forum doesn't make them honest! Be VERY careful of buying anything on UK Buy-Sell without testing it personally!

If you skin the outside of the tube with CF you will lose your superb finish. Won't you?

I missed the Thursday afternoon lesson on electronics. [Back in the last century.] So I use a friction roller and bicycle crank drive on my DIY dome base ring. More recently upgraded with a chain drive to a lower crank within easy reach of my imaging desk. The dome can get up to several hundred RPM in seconds and stops on a dime/farthing. It would not be too difficult to rig up a remote system using a long drive rod from a warm room. Not sure the Pulsar has a drivable base ring.

Regarding slipping timing belts off for manual: I find that most focuser knobs slip smoothly within the toothed belt for manual override. But work just as well with a motor/belt tension adjusted for reliable driving of the standard knob. This is probably due to the timing belt teeth having completely the wrong pitch or tooth shape for the knob. There is easily enough friction for a motor drive but this is effortlessly overcome by the Mk1.5a digits.

Does the drawtube block any light to the mirror's full aperture when the telescope is focused? Protrusion inside the main tube [at full inward travel] hardly matters if it is never seen by the mirror in normal use.

Just as additional information: The elderly usually experience yellowing of the eye lens. Which acts as a natural filter for false colour. So they may more easily enjoy the Sidgwick correction factor. Rather than needing the far more stringent Conrady standards. Personally, I never found any improvement from stopping down an achromat. Whereas I always enjoyed the benefits of a Fringe Killer filter with my 6" f/8. Though not a common No8 yellow filter. My iStar 180/12/16 R35 achromat does not improve with stopping down nor using the "FK" filter. This is probably due to its unique colour correction failing to respond to "normal" filtration.

Auto-guiding is possible with popular imaging software. SharpCap for example. It monitors the image for a while and then "locks on" if there is enough data. No idea if it works on Skywatcher mounts.

I can't even remember the last time I did any solar imaging. Was I there? Thermal agitation and going in and out of focus. 500 frames. SharpCap, AS!3, imppg, Photofiltre. I should have tried the PST blocking filter but stuck with the Lunt B1200S2. DIY 6" f/10 H-a iStar refractor, 160mm Baader D-ERF, PST etalon, ASI174MM.

The only time I might use the Lacerta visually is in the early morning. Hopeless for binoviewing. Doesn't improve comfort by rotating the focuser. It works fine for imaging. For visual I normally [sic] use my 90° Lunt.

Given a suitable, ring form support, it would be quite possible to bolt a sturdy stud [all thread] to the centre of the upper moving platform surface. A compact, lead weight on the stud, placed well below the platform, would lower the C of G quite nicely. The platform base plate would need a slot to clear the counterweight bar. Some commercial equatorial platforms use open frames. While the lead weight would make portability an issue it would greatly improve stability. For larger instruments [Dobs] I could imagine the platform's baseplate or frame mounted on a concrete pipe buried in the ground. With the pipe projecting from the ground only enough for clearance. To avoid lifting heavy DOBs to place them on the platform. The diameter of the pipe would limit the allowable tilt of the upper platform when the lead weight reached the inside of the pipe. Which suggests a cylindrical lead weight for minimum diameter.