Sumerian Optics Alkaid 12"

[LRoulin]

Thank you very much for the update, BGazing.

I'm glad you managed to solve most of your collimation issues, it is indeed a bit tricky on a Sumerian when you're used to "traditional" dobsonians.

As for the stabilisers, please do tell us if they help reduce vibrations when you'll be able to go to a dark site!

Take care!

 

[BGazing]

On 30/04/2020 at 21:47, LRoulin said:

Thank you very much for the update, BGazing.

I'm glad you managed to solve most of your collimation issues, it is indeed a bit tricky on a Sumerian when you're used to "traditional" dobsonians.

As for the stabilisers, please do tell us if they help reduce vibrations when you'll be able to go to a dark site!

Take care!

 

Well, we finally went to our dark site. After two months of glorious skies since mid March (which we spent in quarantine at home) we could finally go, but the weather turned rainy and unstable. Still, Friday forecast gave about 50 percent chance that it will be clear so we took our chance, luckily. It was  clear night, SQM was 21.65 and we stayed for about 4 hrs (we were too tired to stay for more and it was fairly cold at 1000m elevation).

We used C11 and Alkaid, so it was plenty of aperture.

Alkaid did really really well. Before listing what went right, let me tell you what went wrong.

I came early and set up early. In doing so (and because i have not set up Alkaid for quite some time) I forgot to push trusses fully in. This meant that when I had to collimate, I was having all sorts of troubles, including running out of collimation screws (and primary holder going down) etc etc. I finally realized my folly when I saw that the bottom of some trusses is 'smeared' with whatever it gets smeared it when it is fully pushed down, i.e. I did not push them down and the whole secondary ring was offset. Once I naled that, collimation was great. But until that point, I was going back and forth (fortunately not in the dark) so many times that the next day my right knee locked. I also realized that barlow laser collimation is really something to consider in the future, so tuBlug will probably come.

Now for the good. Mirror got cooled down properly, shroud was on, startest showed excellent collimation and concentric circles except for the slighly quadratic rings due to the shape of the shroud.  We killed time until astro dark (22:30) by splitting some doubles, Algieba was particularly nice. Once it turned dark, I started galaxy hunting. Transparency was not that great and some of the favorite targets (e.g. Whale) were lower than necessary. M101 was relatively washed out. M51 was great with lower spiral clear in direct vision and hints of upper bridge. It was like 8 inches but everything better and clearer. Cigar was HUGE, galaxies were viewed mostly around 135-165x. Sombrero a bit low. Triplet was very nice. Black Eye at 200x was excellent, Whale at 165x, Hockey stick and whatnot. I planned a lot of targets but it turned out that the star of the show was M13. I turned to it out of curiosity and it was magical. I have viewed it through quite a few 11 and 12-inch scopes but this was the best M13 ever, no photograph I saw does it justice, jewels of black velvet, so many of them resolved already at 165x. 215x was even better and I was not even using Paracorr (still has not arrived). Mesmerizing. I have to say that this, in comparison with C11 (where I it was not as great) was due to thermal management. It was good collimation, good quartz mirror properly cooled.

In use Alkaid was fine. I pushed power until 215x and at that point tracking (nudging) was not jerky but was not completely smooth, difficult to describe. Stability was good, I was using light EPs (T6s and Pan 24). You cannot just slap the scope around because it is delicate, but treat it delicately and it will not rock around or lose balance. If I missed anything it was a good pair of IS binoculars to couple with the RDF, on some targets it took me a while. It does not help that in 12 inches there are so many galaxies popping out and confusing me and I was a bit lazy at times to go back to Pan 24 for low power finding...

But overall, it was a great night and I am glad I got that huge chunk of mirror. I did not use stabilizers, perhaps next time (June, hopefully).

[BGazing]

A follow up on this. I used stabilizers for the first time just now (I do not know why I postponed that experiment) and they performed admirably. Have to write to Michael to include that as a standard. Collimation of the secondary was much better with altitude change and the laser spot did not leave the center of the triangle as it I moved it throughout.

In the meantime, I managed to bust one of the collimation screws and had to replace it (with a bigger M6 screw (can't find a M5 here to save life), basically the old wood insert had to be drilled out as the collimation screw got completely stuck). Very important: you have to push all the trusses down completely when assembling. If you do not do that you will end up creating collimation problems with the primary and run out of thread or tighten too much. Stating position for all three screws behind has to be 12mm from the mirror cell.

Paracorr is now always in unless I have to observe very low objects.

Attached is a picture of the stabilizers.

Given that Moonlite has discontinued its non-motorized focures, it will be interested to see what will be fitted to Alkaids in the future.

[Jonk]

I like the idea of the stabilisers, I might make some for my Alkaid .