John

None of mine are serious - its a hobby for me and I do it for fun So Peter is probably right in that respect - it depends on the approach and attitude of the owner rather than the scope. When a look back at all the years of observing that I've done though, it's when I've been using my larger aperture scopes that I've been able to go deeper, look futher and see things that I otherwise would have found harder or not been able to see at all. So I guess currently my 12 inch dob is the nearest I have to a "serious" scope despite my lovely (and somewhat more expensive !) refractors.

The exit pupil does reduce as you suggest. I believe that coma is not actually changed because thats already in the optical system from the primary mirror which is still F/4 but sometimes it will appear a little improved because of the narrower field that the shorter effective focal length eyepiece delivers. Barlow lenses increase eye relief a bit too. There are one or two barlow designs around that claim to reduce coma (eg: the klee barlow) but I've not seen overwhelming evidence that they are effective. I've always thought that a coma corrector is either essential or very, very good to have if well corrected wider angle eyepieces are to be used to full effect in an F/4 newtonian.

This pre-production unit came with just one weight.

Ok, I've posted some initial feedback on the AZ100 mount here:

Due to one thing and another I’ve not had time to do more than unpack the packages that this kit came in from First Light Optics and this evening bolt a few bits together. Lots of boxes = lots of FLO’s “May Contain Clouds” stickers and, my gosh, that has proved to be the case so I’ve not been able to actually use this handsome new mount, yet. I must emphasise that the mount that I have been sent is a pre-production unit. The final item may vary in some details from the one that I picture and describe here and in my other reports. My very early impressions of the pre-production AZ100 are: - The AZ100 is significantly larger than both the Skytee II and the Giro Ercole. The pictures don’t really show how much difference there is but the whole mount is much more massive in all respects. - A quick and crude weigh in using a spring balance showed the AZ100 at 8.5 kg with saddles and slow motion controls installed. My Skytee II was at 5.2 kg and the Giro Ercole at 4 kg. - The fit and finish of the AZ100 is excellent. Everything fits together precisely and is machined to a really high standard. Both axes move very smoothly and are consistent in their feel. No sloppiness or jerkiness, just smooth progression around the axis. There are tension knobs on both axes which apply gradual and finely controllable tension. At full tension an axis is firmly locked but a quick twist of the knob and you have movement again. - The slow motion movement is likewise very smooth indeed. I could not detact any obvious backlash when I reversed the direction of travel but I was not looking though the scope at high power of course ! The slow motion control cables and knobs are high quality units and fasten to the worm shaft with 2 grub screws. On this pre-production version of the mount the end of the worm housing opposite the slow motion cable is open but I wonder if a rubber or plastic cover (removable for adjustment) might be a good idea on the final version of the mount ? - The Losmandy-type dovetail clamps incorporate 2 individually tensioned clamps on one side of the jaw with chamfered tips so that the dovetail bar is pressed back against the plate assembly as well as down into the fixed groove on the other side of the clamp jaw. Very secure, that seemed to me. - The knobs on the dovetail clamps and those that control the axis tension are excellent quality with a 5 star shape to give grip. I do wonder if they might benefit from being a little larger though, to help positive operation with gloved hands ? - I have unpacked the counterweight shaft and 5.2 kg counterweight and include a photo of those but I’ve not fitted them to the mount yet. The current design requires that one of the dovetail clamps is removed and the dovetail bar bolted on (4 bolts) in it’s place. The dovetail bar is 25mm in diameter, 28cm in length and it and the stainless steel counterweight are finished to the same high standard as the rest of the AZ100 mount. - My 130mm F/9.2 triplet refractor fitted onto the AZ100 easily and seemed to be very securely held in place. This telescope is 1.35 metres in length and weighs 9.9kg including the tube rings, dovetail bar, diagonal and finder. The true test of the mount will be it’s ability to hold this scope steadily at high magnifications when viewing the night sky ! - First Light Optics have also supplied me with a Nexus DSC Digital Setting Circle unit and a suitable power pack but I’ve yet to fit that to the mount. The encoders for this are already installed in the mount body. - Both the tripods pictured are the Berlebach Uni 28. Mine is the slightly darker coloured one with single leg clamps and an HEQ5 fitting. First Light Optics have provided an EQ6 compatible version of the tripod which is fitted with double clamps on each leg. The AZ100 mount fitted snugly and securely straight onto the EQ6 hub. - The combined weight of the Berlebach Uni 28 tripod and the AZ100 mount head is around 18kg. It is a well balanced combination though so I can move the mount and tripod setup around without too much trouble. With the 130mm refractor on board, it becomes somewhat more of a challenge but I think moving the whole setup short, level distances (ie: a couple of metres) is likely to be feasible with care. I apologise for the rather hastily taken photos that follow, taken in the rather messy setting of a dining room which is currently being re-wired and re-decorated completely. I’ve included the Skytee II and Ercole Giro in a couple of the photos to give an idea of the comparative sizes of these mount heads. More to come in due course including experience under the stars, hopefully in the not too distant future ! Many thanks to the folks at First Light Optics and Rowan Astronomy for allowing me to try this pre-production version of the AZ100. It seems to be a very impressive piece of kit with excellent attention to detail and a very high standard of fit and finish. Meanwhile outside, the rain pours down tonight so have a look at some pictures

I've used one of the Skywatcher 150 F/5 newts on an AZ-4 mount head and it worked pretty well. A Giro or a Sabre would be more than adequate I'd have thought. The AZ100 would be overkill (but in a lovely way !) IMHO

Spinal Tap ?

Some more great points of view have been posted in this thread. Thanks very much for contributing what you think folks I didn't set out to start an observation vs imaging thing of course. Whatever floats your astronomy boat is good with me The majority of members of my astro society don't image or observe but I enjoy meeting and talking with them anyway.

Sorry folks. I have checked the contents of the packages (all fine) but I've had no chance to assemble and play with anything due to extensive DIY work going on here. I'll try and get some photos taken when I get a chance. Weather forecast looks poor so actually using the mount may have to wait a bit longer.

...... and then a coma corrector because the better corrected eyepieces will allow the coma that the scope produces to be seen more readily

Looking at your eyepieces (assuming these are what you are using) you might be seeing astigmatism rather than coma. Coma will also be there but eyepieces that stuggle with the F/4.5 focal ratio will show astigmatism in the outer field of view which tends to mask the coma and/or combine with it. A coma corrector will tighten up edge of field views by controlling the coma but won't address eyepiece astigmatism if that is the primary cause of what you are seeing. Some more info here on these issues to help you decide what the issue is: http://umich.edu/~lowbrows/reflections/2007/dscobel.27.html

Thanks for the link - I'll have a play with that I believe it's really called Barringer Crater after Daniel Barringer who was the 1st to propose that it was created by a meteorite. It has also been known as Canyon Diablo Crater after the narrow, sinuous dry valley that winds across the plain nearby. The meteorite that created the crater is still known as Canyon Diablo. The Barringer family still own the crater and some land surrounding it and operate the visitor centre and access to the crater. Frankly for $18.00 I thought it good value but then I'm into astronomy

Which flare outwards towards the primary I seem to recall so they would be the true secondary obstruction of the scope I suppose.

Good point from Steve regarding the status of the mount that I have been sent. I will repeat it when I'm posting on the mount to avoid any confusion. I'm pleased that Stu will have a crack at it too - his experience and enthusiam for the technology side of things is much greater than mine I'm unwrapping the mount and other accessories now and will post some photos and initial reaction ASAP. Many thanks to Rowan Astronomy and Steve / FLO for trusting me with the inital "tyre kick" of this product

Nice specimens of Sikhote Alin folks. My own bit looks more like Debo's to look at but a smaller piece. I used to have a wonderful 200 gram chunk of SA with reglamypts, a roll over lip and other flight markings. I sold it a few years back to buy more astro stuff though I've been building up another meteorite collection recently - I'll have to post some pics. I'm up to 20 different types now.

Thats good to know Chris. It must have been the earlier ones that were working at less than full aperture. Neil English was convinced that his (branded Orion USA) was nearer to 170mm and referred to it was such in his review of the scope. This is an extract from that review: "It was discovered that the effective aperture of the large Orion Maksutov was nearer 170mm than 180mm. I was alerted to this after performing double star tests earlier in the summer of 2014. When I observed Zeta Herculis, I detected the faint companion to be located on the first diffraction ring of the primary star. Now, the locus of the first diffraction ring from the Airy disk is 185/D where D is the aperture in mm. The latest information on its angular distance from the primary is 1.1″. Something interesting occurred to me when I set the formula to find D for a 1.1″ separation. Thus 185/1.1 yields 168.2mm. Then I remembered a review on a lady’s website from the UK where she talked at length about the same (albeit Sky Watcher incarnation) telescope and reckoned the actual true diameter was nearer 170mm than 180mm; "Subsequent flashlight tests confirm that many of the Synta/Orion Maksutov have slightly smaller apertures than advertised (the 127mm model being closer to 120mm). This is due to the fact that the primary mirrors are the same aperture as the corrector plate which results in slight internal vignetting. In comparison, the older Meade 7 inch LX 200 Mak as well as the Questar 7 have an over-sized primary mirror to correct for this." Presumably Synta must be incorporating a larger primary mirror with the later models ?

Thanks Steve, It was great to bump into you and your other half at the Lowell Observatory. That was another place that I'd wanted to visit for many years

Hi and welcome to the forum The focus on a finder is usually adjusted as per the movie that Knighty2112 has posted. The standard 50mm finder on the Orion XT10 is a stright through unit I think - the 45 degree prism / eyepiece is likely to be a later addition. If the 45 prism / eyepiece has been added to a stock straight through finder then that might be a reason why the finder will not come to focus.

Are the Skywatcher mak-cassegrains operating at full aperture these days ? Their design used to mean that the effective aperture was a bit less than stated so the 180 was in fact a 170 etc etc. I had a Skymax 180 for a short while but found the cool down time too long for my observing circumstances.

You can always experiment with a cardboard mask with a hole the diameter of the clear aperture of a 1.25 inch filter cut in the centre. Put that on the end of the eyepiece barrel and see what the effect on the AFoV of the eyepiece is.

Thanks. There is a nice and newish visitor centre and museum which leads on to viewing terraces on 3 levels and there is also a walkway partway around the rim. To get down to the crater floor is a 2 hour hike in very hot and rough conditions. Only allowed by special permission. As you approach the crater (the pic below was taken from around 3 miles away) all you see are the low crater ramparts, no suggestion of the massive pit of the crater which is 1200 meters across and 175 metres deep. All created around 50,000 years ago in around 10 seconds by an iron meteorite estimated to be around 150 metres in diameter. Must have been quite a BANG !!!

Seems a long time ago already but a month ago I visited this place which has been on my "must do one day" list for many years. Very much worth a visit if you are ever in northern Arizona

I'm going to spray my Skytee II black, pop it in the AZ100 box and hope they won't notice the difference ........

I believe so. I'm expecting this setup when I unpack the packages on Monday. Plus a Berlebach Uni 28 tripod, a power supply and a Losmandy plate to attach the scope that I'll be testing the mount with. What nice people they are

The coatings on the lenses could get scratched and that would notably devalue the eyepiece if you ever want to sell it, although it would still work fine.