gorann

I would not mind Chroma filters for my other scopes and cameras but they will not work on fast scopes like the RASA. Only Baader seem to bother making such filters, and In this case it is probably not a Corona issue since Baader as I understand it make their filters in Germany - they just need to produce a batch that passes their QC.

Well, this is the situation with everything since Corona, and with filters everything is made in batches. If you go into the TS site you can at least get a dlivery date (15 Oct for my Oiii, although I have them ordered from FLO). I have the Ha and I just ordered the Sii that is on its way in the mail (saw that TS had them and ordered now to be safe before it runs out).

Yes. that will elliminate any diffraction spikes, so go for it if you settle for a RASA. I made mine from garden-plant wire and electric tape, but your fiend's alernative looks more professional and 15 USD is not much to complain about. Regarding heating from the camera I never heard it would be a problem and maybe the camera fan just creates enough air flow to dissipate any gradients that could act optically. Just like fans at the back end of RC and Newtonean telescopes.

Or find a way of powering the camera without cables - I think there is technology for that (have it in my electric tooth brush charger). Then it could send out the data using Wi-Fi.

Interesting Olly. If I ever buy a Newton it will be one with curved vanes - why do not more offer them or maybe they can be retrofitted? I never liked star spikes (must be a Hubble fashion) and they do not make it easy to combine new and old data.

I never heard it mentioned as a problem by someone having a RASA. As I said the heat from the camera works to your advantage by slightly heating the corrector lens so you do not need a heater, just a dew cap (although I still have to see what happens when I get into sub zero temperatures in a few months).

That is an excellent result Richard. The "radioactive" star issue is really minor. You clearly got the right chip distance and no tilt since the stars are nice and round over the whole field. Come to think of it, you must have done this under a nearly full moon - that is extraordinary.

I dont think a FW could ever be fitted infront of a RASA 8. Maybe on a RASA 11 or the astronomically expensive RASA 14. but it would be quite an obstruction. With a FL of 400mm, an OAG is really not needed, a guidescope is good enough. One way of doing it with a slider would be to collect RGB before you go to bed and then let it collect Lum for the rest of the night. My plan is to do bicolor HaOiii by swapping filters just before I go to bed.

I think you could be right - at least a big refractor wins in sharpness but loses in FOV and speed. I doubt that a 400 mm FL refractor would be much sharper that a 400 mm FL RASA unless possibly you go for really long integration times with the refractor. With the same integration time the S/N ratio of the RASA should be much better. But if I do a mosaic with my Esprit 150 with relatively long integration time, it would proably be sharper and more pleasing to pixel peepers, but after Tomato @tomato saw my RASA 8 image of M31, he gave up his plans of doing an M31 mosaic with his double Esprit 150 rig and bought a RASA 8! When weather is like it is, then speed is an important factor.

You need the Baader UFC Universal Filter Changer System made for the RASA - FW is not possible. https://www.firstlightoptics.com/baader-filters/baader-ufc-universal-filter-changer-system.html

Cable diffracton spikes can be easily overcome by organizing the cables in a circle. Since I did that I cannot see any spikes. I had not heard that heat from the camera would be an issue. Maybe the fan in the camera will create enough airflow to avoid this. I rather see the camera heat as an advantage since I do not need a heater band to protect agains dew on the corrector plate (I certainly need that on my SCTs). The camera heat, in combination with a dew shield does a good job of keeping the dew away.

I dont think you could compare the RASA to the Starizona hyperstar add-on which just seems to be a lot of trouble.

630 dollars for the tube rings! I find no scale on the spot diagrams. Can you interpret them? Tak has published these spot diagrams for the Epsilon 180 on a 50 µm scale (side length of the squares) and it suggests a similar spot size to the RASA

Found these spot diagrams for the Sharpstar 150 Hypergraph (from the Teleskope Service site - bottom image) and RASA 8 (top image from a Celestron booklet, file attached as pdf). Note that the one for Sharpstar is on a 100 µm scale and that the one for RASA 8 is on an 18 µm Scale, so its seems to me that the RASA is about 5-times sharper. Make sense that Sharpstar chose to present the spots at a 100 µm scale. However, I am no expert on spot diagrams so maybe I am missinterpreting them. RASA-booklet-8in-11in-36cm-pdf.pdf

Thanks Wim - I had planned to sleep all night last night, but glad I didn't. Now it is raining...

Hold your finger! Here is another thread you should read - apparently the Sharpstar optics are far from sharp but quite fuzzy (bad spot diagram) compared to the competitors, when it comes to astrographs they are Tak Epsilon and Celestron RASA. https://www.dpreview.com/forums/post/63734509 For the same price you get a RASA 8 f/2 with much bigger aperture (collects twice as much light), better spot diagram, and no collimation issues, at least not for me. I got one for this season and I am very happy with it so far. You can read some of my recent threads: PS. With the RASA 8 you cannot use a DSLR but need a dedicated circular astrocamera (like an ASI) - I don't know what camera you have or what your plans are.

Thanks Xiga! Yes, for some reason this quite exciting object has been generally forgotten, maybe because of its neighbour. I would also like to get Oiii for it but the high-speed filter I need is not available until Baader finishes the new batch (hopefully in October). Since Corona everything in astrophoto are on back order, but I guess that is a minor probem in the big scheme of things.....

Works perfectly but I should not get all the credit. Curves do not create spikes and Vixen are selling scopes with curved spider vanes.

The moon is out so I am collecting Ha with the RASA 8. Sh2-119 is that less commonly imaged nebula to the "left" of the North America Nebula. Collected over two nights this weekend as I only got 40 min the first night due to uninvited clouds. Totally 68 x 5 min with ASI1600MM on gain 139, offset 50, cooled to -20°C. Frustrating to wait for the moon to go away before I can collect RGB for this object

That is a really great story and the very best of luck to you - it should be a success! What camera are you putting onto it. I have the same OTA (allthough on an EQ8 and much less impressive pier) and I am quite impressed with the optics - it can cover 24 x 36 mm with a flat field and without much vignetting.

I just wanted to point out that there is now an affordable option for a fast "astrograph". It is without star spikes or other artifacts (they disappeared with my RASA after curving the camera cables, as others have found before me). Not sure that there is a difference in the "crispness" of stars and how that would relate to the difference in optical systems. I have recently entertained myself with pixel peeping stars in Epsilon and RASA images on the net and as far as I can see there is no clear trend - just good or less good ones from each scope/processor.

Yes, that is true and slipped my mind. However, now thinking about it, the effect is not very large, but very expensive. The Epsilon 180 (that has 80% of the aperture area of the RASA) has a FL of 500 mm (RASA 8 is 400 mm) so with a 36 x 24 mm chip, the Tak only gives 23% wider FOV than a RASA with an APS-C chip. With ASI cameras the cost (FLO prices) for the two set ups will be 1839 (RASA) + 2069 (ASI2600) = 3908 pounds and 4345 (E 180) + 4159 (ASI6200) = 8504 pounds. Maybe it is worth it?

Interesting and sorry for intruding on the thread, but I did not know that the Epsilons both have spikes and clip reflections. Here is Sadr in my RASA from two weeks ago (same camera). I was close to getting an Epsilon until a good offer for a RASA 8 came up and I am getting curious about the advantages/disadvantages of these two popular wide field designs. There is certainly a big price difference.

Thanks a lot Mark. Yes, I've Oiii on order from FLO since July but Baader is still working on the next batch of fast Oiii filters. Everything seem to be in short supply right now.....

Thanks Richard, much appreiated! Have had a good run with my new RASA 8. Finally clouds have moved in so I can get some desent sleep🥱