gorann

A great relief to see that you finally got round stars Olly! Regarding oval star halos I have also noted that in some of my RASA images and suspect it could be related to the curved camera cables, so a kind of soft star spike, but that is just a guess. Just out of curiosity, maybe you can have a look at what angel your cables lie in relation to this slight halo effect. In any case such a small halo distortion is easy to live with.

Here are two pics of my adapter that may help you. The holes I drilled was in the FLO adapter to fit the holes in the FD-EOS adapter (after I unscrewed the EOS part). You also see a M48 to T2 adapter and a distance ring in the pics (adding 14 mm) screwed on to get the right distance. Lens flange to chip distance for FD lenses is 42 mm, and the chip distance in the ASI2600 is 17.5 mm. The adapter I made was 10.5 mm thick so I had to add 14 mm to get to 42mm. Cheers, Göran

Great start Olly & Paul! when you get 100 of those subs stacked, then the magic starts for real!

Hi Thomas, I could not find anyone selling such an adapter so I made one by taking apart an EOS-FD adapter from ebay (image below) and attaching it to this adapter from FLO: https://www.firstlightoptics.com/adapters/astro-essentials-samyang-lens-to-m48-adapter.html Had to drill three holes and put it together with three M1.6 screws and nuts. Cheers, Göran

Thanks for the encouragement Jessun.

It is not only us and the IKO data that swings that star towards blue, I just saw this post by Skarpen on Astrobin: https://www.astrobin.com/w399qv/ But as Wim points out - our main goal is to make pretty images😁

In several of the images here I notice a curious error in the colour of a particular star situated at 8 o'clock in relation to the core of M81. Many people got it blue and in the data I found that there is a bluish halo-like area around it. But when I saw Vlaiv's version (small crop below) of the image I noticed it was yellowish, and Valiv made an effort to get the right star colours. So I looked up that star in Aladin SkyAtlas and it is HS85458, which is a F5 star so whitish-yellow. I wonder why the data easily makes us drift over towards blue on that star. Maybe it is the bluish area around it and maybe that has no connection to the star. Cheers, Göran

Would that be more problematic in a dual rig? In any case I never noticed any primary mirror movement before, such as loss of focus or image drift/shift. The RASA is claimed to have a different and more stable mirror holding mechanism than the ordinary SCT.

Interesting discussion here about bracing arms. I will consider it if I notice flexure. After @Sp@ce_d here pointed out that the max imaging weight of the CEM70 is stated to be 21 kg I decided that I will move the rig to my Mesu 200. That mount is also sitting in an obsy with more floor space which will make everything more comfortable. I will be traveling for the next week so it will take a while before I can give the rig a try, skies permitting.

Interesting but the attachment to the rim may make it difficult to fit the dew shield that is absolutely neccessary for a RASA. It is easy enough to curve the cables by tapeing them to a curved metal wire and let the cables out of the slit of the dew shield as I do. And with the FLO thing you would have to lead the cables down along the side of the camera which could make them casue spikes since the diameter of an ASI2600 is the same as the central obsruction (90mm) so you do not want anything to stick out.

It is obviously a worry if I cannot tell the mount in some way that I have turned the saddle 90°. I have to look into that. Maybe my Mesu is the only option. Maybe someone with a CEM mount have a suggestion.

you mean like this one. It says 4-6 working days, the same as for the Zarkov Cloud Gun. Could be a code..... https://www.firstlightoptics.com/optical-tube-assemblies/celestron-rowe-ackermann-astrograph-rasa-8.html

Both of you have good points. Thanks! Now there is only one way to find out🥴

My Esprit rig is a 150 with OAG and a 100 next to it. The relatively short tube and short FL of the 100 probably help to reduce any problem with flexure. I can see the necessity for a bracing plate with two 150s.

Nice, and you are well on the way but may need more data. I do not have any DSLR version of it but I have two HaOiii images, one up close with my Esprit 150 and ASI1600MM (7 hours w Baader filters), and one wide field with a RASA8 and ASI2600MC (6.5 hours with IDAS NBX dual band HaOiii filter). Cheers, Göran

Thanks Wim for pressing me to finally put it together! I am not too worried about flexure since I use an identical rig for my Esprits with longer FL and never had a problem (or at least never realized I had a problem). I did think about it and I think it would make it difficult to do separate framing with the two scopes. Maybe it could also induce some tension and distort the shape of the tubes. In any case, to find out I need a counterweight and a clear sky🙂

Yes, maybe that is easier. Thanks!

I am excited about what will come out of Les Granges, and slightly worried about what Hole Obsy has got itself into🤔

Yes Steve, I expect I can use the saddle to get mosaics with 10-20% overlap.

Exactly. It is probably only for a month each year that I could get half decent data so maybe I should leave it to the southerners.

That is a great image Rodd! Reminds me that I have not aimed at it since I moved from DSLR to proper cameras. I remember processing was tricky and of course the end result was nowhere near as good as yours.

Just got the dual rig up and realize I need more counterweight. I wonder if I may double the trouble rather than the integration time🥴:

Thanks! With one of them sitting on an adjustable saddle it should be possible to take two images next to each other, either above or below the other so the aspect will be close to the "standard" 4:3, or side by side for a panorama. To some extent I should be able to maybe point at two separate object but they cannot be too far apart (not sure how much flexibility there is in that adjustable saddle). Yes, I think I have also seen that Sharpstar 130 quadruplet somewhere. I wonder how they solved the alignment - must be adjustable somehow. Doing a quadruplet RASA is apparently possible: And even more but them we get into professional territory: https://www.dpreview.com/forums/post/62471743

Thanks Tony! It is this one: I do not know of any other brand making such adjustable saddles. https://www.firstlightoptics.com/misc/jtd-dual-rig-telescope-alignment-saddle.html

I am so amazed by the RASA 8 performance that I bought a second one this spring. Initially I have been using the first one on an iOptron CEM70 mount and I put the second one on my Mesu 200, so in two separate obsies here at my little farm. But I rather use the Mesu for some of my other scopes so I decided to make a double RASA 8 rig and put it on the CEM70. One of the RASAs have an Evostar 72 as guidescope and I put a piggy-back scope on the other: an old Canon FD 200 mm f/2.8 I found cheaply on e-bay with an ASI2600MC. I have ASI2600MCs also on the RASAs. The whole shebang put together turned out to weigh 29 kg so I may really be pressing that mount (iOptron claims that it can take on 32 kg but maybe that is visually). I put it up on the mount today and realized that I need at least one more 10 kg counterwieght, which is now on order from TS. I just hate the price of counterweights😬. If the iOptron cannot handle it well enough to give me reasonably good guiding, plan B is to put it all on the Mesu 200. I will find out when I finally have enough counterweights to balance it. Why two RASAs one may wonder? My idea is to either make instant 2-panel mosaics, or collect HaOiii (IDAS NBZ filter) with one and RGB with the other. Or just double the integration time I can get in one night. Cheers, Göran