John

I think the F/6.3 reducers are designed for use with 1.25 inch format eyepieces. With 2 inch eyepieces and large field stops they vignette the field of view I believe.

That's the point I was making in my post earlier. Observing with some aperture at really low magnification and with a wide angle of view shows patterns etc that we ordinarily don't notice or can't see because we are looking through them, as it were. It's a bit like seeing aerial views of a place that we think we are familiar with

Apparently, Sirius B is a little smaller than the Earth but it's mass is very nearly that of the Sun !

Optically, the introduction of the Schott glass stickers on the tubes of the black diamond versions caused some confusion. Apparently Synta have always used Schott glass in these and their ED doublet refractors (as the mating element to the Ohara ED element) but entered a revised marketing agreement with the glass maker Schott which resulted in more overt promotion of their glass product.

I think the mak-cassegrain 127 will show DSO's as well as any other 120mm-ish aperture scope will as long as they will fit into the max true field of view that the design can deliver which is a bit over 1 degree. Lots of DSO's are smaller than that.

Lucky you Michael Are you going to have a go for the supernova as well ? Here we have yet another night of thick dark clouds with intermittent fine drizzle

If you can get a really low power and wide field of view with a scope It's amazing what shapes and patterns you start to see that you didn't notice before. I like to browse around the double cluster in Perseus with my 102mm refractor at 20x magnification. There are all sorts of star chains, shapes and loose line of sight associations around that part of the sky. I don't know if the term "rich field scope" is still used but there is certainly a place for instruments that can excel at this IMHO. Interesting article by Mel Bartels here on this topic: https://www.bbastrodesigns.com/rft.html

Not an ED100 but I have tried my Takahashi FC100-DL on the AZ-4 (it is a similar length and weight to the ED100) and Personally I thought the mount vibrated just a bit too much at high magnifications for my liking. That might be a personal preference though. Other might find the combination is OK.

I don't own either but having used an Evolution mount (with an 8 inch SCT) I would think that clearance between the focuser end of the FC-100DZ and the mount base might be an issue when the scope is pointing above 45 degrees altitude ? In this thread on another forum, this is discussed and modifications are shown which allow a 4 inch Takahashi to be used with an Evolution so that it clears the base: https://www.cloudynights.com/topic/632855-refractors-that-work-with-evolution-mount/

Having owned a couple of AZ-4's I think you are right to be cautious over the length of the scope you put on it. I found the F/9 refractors (ED120 and Tak 100) just a little bit too much for my AZ-4's but my Vixen 102 F/6.5 is very happy on one even at high magnifications. A 102mm F/7 would probably be a good refractor choice (ED doublet). Something like this (when back in stock): https://www.harrisontelescopes.co.uk/acatalog/altair-starwave-102-doublet-refractor.html#SID=1706 Altair do a 102mm F/11 in as well but I do think that tube length would be too much for the AZ-4 Here is my Vixen ED102 F/6.5 on the AZ-4 - a nice combination:

That makes the point ! Thinking back, the SCT's that I've owned have been collected from the seller myself so not put at that risk. The meniscus of a mak-cassegrain is quite a lot thicker than the corrector of an SCT.

I use the Skywatcher and Celestron RACI's on my scopes. 9x50's and 6x30's. They do a good job. Similar quality to the Astro Essentials one I would think.

I guess it depends just how tight your budget is. In terms of the actual views you will get, both scopes will deliver very similar performance. The Skywatcher is hardly a poor prospect - there are many, many happy owners of the Skywatcher dobs on here and around the world.

I agree with the other posters - if you can get the ED150 it is a much better scope or even an ED120. I've owned a few of the Evostar 150's and they have been fun scopes but I would not pay £500+ for one.

I agree that maks are can be sharper than SCT's. I've owned several of both types and the build seemed solid on all of them. The Skywatcher, Celestron and Orion (USA) maks are all made by Synta as are the Celestron SCT's now, at least the ones under 11 inches in aperture. Possibly those as well now. Even Meade seem to be selling a Synta made mak now: https://www.meade.com/telescopes/maksutov-cassegrain/lx65-mak-6.html

Mak-cassegrains can need collimation tweaks as well and are also challenging. There is probably more stuff written about SCT collimation. Refractors as well, I've found, sometimes need some collimation adjustments. 150mm F/8 dobs also benefit from collimation tweaks but are a lot less expensive than either the SCT or the mak-cassegrain of the same aperture. If DSO's are the primary interest, aperture makes such a lot of difference so the 200mm f/6 dobs, or even larger, do make a lot of sense.

My sky is bortle 5, sometimes 6 (depends which direction I look in !). I recently had the Explore Scientific UHC for a while. It was not that effective I thought. I have now got an Astronomik UHC and find that having more impact on responsive targets. I will still use the O-III (Lumicon) more I think but I feel that a good UHC like the Astronomik will earn it's keep. I think the band pass of the ES UHC was a bit to wide which reduced the impact that it had.

The Orion that you are looking at is a Synta product as Louis says, nothing to do with Orion Optics of the UK. I think the Orion USA 150mm mak-cassegrains are the same as the Skywatcher Skymax mak-cassegrains so comments on the 150mm Skymax should apply. Orion Optics UK do make cassegrains but theirs are 140mm and 200mm in aperture.

The original poster has not been on the forum for well over a year now so I suspect they have moved on to other things. I still have my Skywatcher ED120 and Takahashi FC100-DL though

I use 6x30 RACI's on my 4 inch refractors and 9x50 RACI's on my larger fracs and my 12 inch dob. I seem to have developed a collection of these things !

Observation report here of this SN and others. Sounds a good prospect even without NVD:

Great report Alan Can't wait to have a crack at 2021j myself. Actually a crack at anything would be nice ! Mag 14.5 or brighter is doable with my 12 inch dob without NVD.

There are low profile diagonal units around. Celestron use one on their illuminated RACI finder and the Meade ETX scopes had a low profile diagonal that screwed straight onto the back of the scope. An eyepiece with the focal plane well below the "shoulder" would help as well eg: the Tele Vue 40mm plossl.

Inward travel is what is needed but quite a lot of it. Probably more than the helical focuser can manage.

It's nice to be able to experiment with different filters on different targets to see the effects. Alternating between no filter, a UHC, an O-III and an H-B on Messier 42 for example shows some really interesting differences in extent, the enhancement and sometimes the diminishment of the various parts of this complex target