Ricochet

@Buzzard75 how long do you feel you need to allow the telescope to stack to get a "good" image? What if there are clouds? Does a cloud drifting across the field of view put you back to square one?

If you can achieve focus with a more powerful barlow then that would usually be the better way to go as it will narrow the light cone entering the binoviewer and reduce prismatic effects. However, with my binoviewer I see some additional reflections with the more powerful barlow so you may find that smaller eyepieces are preferable in that instance.

I observe without glasses so eyecup up. I believe it is radiative cooling of the eyepiece outer skin. Because the delites are all metal there is a conductive path from the glass all the way to the exterior of the eyepiece. In effect the eyepiece becomes a heat sink for the eye lens. With the XWs the rubber/plastic covering breaks that conductive path. The rubber still radiates to space but does not absorb that lost heat from the interior of the eyepiece. Similarly, SLVs and Starguiders don't suffer despite being significantly smaller but the larger 21E does. I think using my observing hood also helps as it hangs down over the eyepieces preventing radiation, but this requires further testing.

I suspect this is because your air is a lot drier than mine. During the last few weeks of summer my Delites have been fine but at all other times they have issues. Comparing the time you can have an eyepiece in the focuser it's minutes for the delites vs hours for the XWs. All I can do is report back what I have found using the eyepieces that I own. You cannot claim that I don't see this difference.

No, the 24mm SWA/ES68 does have a bit of field curvature. What it has less of than the 24 Pan is rectilinear distortion.

Based on my XWs (7, 10, 14) and delites (13, 18) you gain a smaller, lighter eyepiece that you are more likely to be able to binoview with the eye cups up. In terms of viewing the Delites are exactly the same as the inner 60° of the XWs, you're just missing the outer 10°. I find that the XW eyecup is more comfortable to use, and it stays at the set height. The XWs are also more resistant to dewing.

Don't buy any eyepieces until you have found barlow/gpc solutions that allow you to focus your telescope with the binoviewer. Once you have a combination that works you can use drift timing to calculate the actual multiplier that the barlow is working at, and from that calculate what eyepieces you will need to buy to get your preferred magnifications.

I used to have 8 and 12mm Starguiders to use with my 8" dob. A 2x barlow and the 8mm worked well for showing Neptune and Uranus as disks but I recall that for Jupiter and Saturn a 7mm X-Cel LX was usually the sweet spot over the 8mm Starguider or the barlowed 12mm. Unfortunately, although I sold that 7mm for about £40, prices have gone up so even second hand it is probably over budget. The barlow option is more cost effective because it gives you two new magnifications, but the 300x magnification is something you will rarely use as Jupiter and Saturn are by far the most interesting planets to observe. If you do choose a barlow the there is nothing wrong optically with the Astro Essentials barlow at £25. The Starguider barlow gets you a more solid build quality and a compression ring instead of just a set screw for clamping the eyepieces. The 58° "Planetary" eye pieces are probably the most comfortable budget option at 6-7mm. The 6mm Baader Classic Ortho will be optically better at £49 but the eye relief is very tight. The eyepiece now sold as the Stellalyra 55° LER was the intended 6mm option in my original plan but I never got around to buying one and have since moved on to binoviewers for lunar and planetary.

The 72ed certainly fits the bill for that. When I started looking at the stats the F7.5 80ED is quite a bit bigger than the F6 72ED. An alternative option which falls between the two is the Stellamira F6 80ED.

1200mm. I find diffraction rings are really apparent at sub 1mm exit pupils. I've got a 2x telextender that I can use for higher powers of needed but I tend to prefer not using it.

I have 7/10/14 XWs. In an f6 scope this is all that is really needed for DSOs, but maybe I could add a 5 at some point. I have Televue Delites and Panoptics. The APM UFF series would be a cheaper alternative.

I recently went for a 72ED as a grab and go for those nights when I haven't got the energy to get my 8" dob out (and put it away again). I considered several 80-90mm ED scopes but in the end the weight and maximum field of view were probably the things that swung the decision. I have been very impressed with it optically so far, lunar views are sharp and it can take quite a high magnification relative to its size. Of course a bigger aperture would show more with regards to DSOs but that also means a longer an heavier scope, potentially with more substantial mounting requirements.

I don't have any experience with the APM XWAs but I do have a 21 Ethos. Initially after getting the Ethos I thought that I would end up moving from XWs to Ethos at all focal lengths when using my dob. However, after a short while I discovered that while the Ethos is good for maximising the field of view I can get through the scope, when examining DSOs for an extended period of time at shorter focal lengths I prefer the XWs. I find the XWs more comfortable to use, don't find myself wishing that the FoV was that bit wider, and due to the rubber covered exterior and longer eye relief they are much more resistant to dew which makes them more suitable for longer viewing periods. I have also used them for lunar/planetary and they are excellent eyepieces for that, although I have now switched to physically smaller eyepieces for planetary as I use binoviewers and I found that I could not use XW pairs with the eyecups extended. I also have some SLVs that I use with my solar scope. Whilst they are very nice eyepieces and give views that are similar to the XWs, I find the 50° field too restrictive for DSOs and as such would recommend wider eyepieces when you are monoviewing rather than binoviewing.

Is it optically better than the standard 50mm RACI? Was the upgrade worth the money?

It's quite difficult to tell what's going on there. I think maybe the secondary is slightly rotated away. The secondary shadow gives it away the most. Do you have a cheshire/sight tube or concenter? You really do need one of those tools to collimate the secondary, a collimation cap is really only of use for the primary after the secondary is collimated. With regards to getting a sharp focus, there are also other factors that can have a far greater effect than collimation so don't get too hung up over it. What eyepiece(s) are you having trouble focusing with? Is it the standard 10mm MA supplied with Skywatcher scopes? If so I would suspect that to be at least part of the issue. Are you giving your scope long enough to cool down before trying high power observing? You will probably have tube currents in the scope for at least half an hour after you get it out which will impact the views. What are you putting the scope on? Concrete and the like hold on to heat for longer than the garden lawn and with the scope being so close to the ground, ground thermals are going to be more of an issue. What are you observing over? If you're pointing your scope over buildings then again thermals coming off the buildings are going to cause problems. Trying to observe when the Moon is over fields or gardens will improve things. If you are observing over buildings, moving your scope back as far as possible so that the Moon appears as high over the rooftops as possible will be useful.

As an update, "long term" was less than a week. It's a Baader BBHS prism ( courtesy of @Deadlake) with a Clicklock reducer, 2" nose, 15 and 7.5mm T2 extensions. It focuses near the end of travel with enough in focus for the BHZ and/or my 2x focal extender. It weighs about 330g compared to 530g for the 2" diagonal and reducer combination. It doesn't sound like a lot, but with the scope only weighing 2kg it has greatly improved the balance issues I was having. I was a bit wary of issues using a prism with a reasonably fast scope but I've not noticed anything untoward yet and if anything it is sharper than the mirror diagonal. I also upgraded the 2" draw tube clamp to FLO's compression band version, which is a great improvement over the stock clamp. Somehow, despite the two clamps looking like they are the same length, the new clamp prevents the BHZ from reaching focus when used with the 2" diagonal and reducer but I may be able to solve that with the spotting scope modification ring or just by using the BHZ in 2" mode on nights where I want really wide fields.

I've just bought a 72ED and the inside of that is what I would consider a dark grey like you describe their Newtonian insides. In fact I've just been inspired to dig through my astronomy drawer for the small piece of flocking left over from when I did my (Bresser) dob. The inside of the OTA could do with some attention too but I'll have to figure out how the lens cell comes off first. However, if they are going to scrimp somewhere I guess it is better that they scrimp on something I can fix rather than the quality of the optics, which so far seem very good. The inside of the dew shield showing the difference between the flocked area and the original paint (hidden under the lens cell when the dew shield is screwed back on).

Great news Giles. If the collimation was that far out you will probably notice an improvement the next time you use the scope.

That's a great change. Now I've seen the difference I'm sure I'll start spotting things that could do with being a darker black.

If it isn't readily obvious when you push on the collimator all I can think of off the top of my head is to tighten and loosen the different clamps and to watch for which ones lead to a change in the position of the laser dot. With my bresser dob I had a problem when I upgraded the reducer to a Clicklock because the 2" clamp was almost entirely a compression ring and the reducer had an undercut, which meant the reducer would be tilted as the compression ring tightened. I upgraded the 2" clamp to solve the problem, but the parallizer would have also solved the issue if I was only concerned about 1.25" eyepieces.

You need to work out which part(s) of the focuser is causing the wobble. If the issue is in the draw tube or 2" clamp a better reducer won't help.

The scope is on rings so the focuser can be positioned in any orientation. However, most mounts are side-mount so to avoid any clash the focuser would have to be orientated vertically and so the focuser would end up behind the eyepiece. I'd prefer a horizontal orientation if possible but I will trial vertical next time it is clear. Also a vertical orientation would probably dictate a right hand mount so that the finder isn't under the scope or clashing with the mount.

Testing my new 72ED has shown that my Starwave Mini mount isn't really up to the task. Weight wise it's fine, but the problem is the distribution of weight. With the 72mm objective being so light, all the weight is at the back of the scope and so the alt clutch has to be done up really tightly in order to prevent the scope from unintentional movement. Would a Scopetech Zero or any other lightweight mount be more able to cope with the rearward weight distribution? Even with a longer dovetail I couldn't really move the scope forward any further as the focuser wheels would come into contact with the saddle.

Good news! It was clear last night and I discovered the telescope actually comes to focus with significantly more room to spare than I was expecting. Using the 2" Clicklock diagonal and 1.25-2" clicklock reducer the 24 Pan and Delites focused with about 10mm infocus to spare and XWs and 21E (without reducer) a few mm further in. The Baader Hyperion Zoom was right on the limit at about 1-2mm depending on the zoom setting. A smaller diagonal is probably on the cards long term to save weight if I find that I do tend to go out with just the 24 Pan and BHZ.

I think the problem stems from it only having 38mm of travel (!!). They must have designed it to work with the flattener + camera and perhaps their diagonal with a shorter light path. Thanks for the link/graph, I was hoping someone might have taken some measurements. I was looking at the Baader T2 prisms and coming to the same conclusions. I've got some Baader T2 extension rings somewhere so I think I could make up a diagonal with a 2" nose and the 1.25" Clicklock that would work nicely and hopefully be a bit lighter too. It would be a shame to lose the ability to use 2" eyepieces and max out with a 5° field but I don't think a 21E is an eyepiece that fits in a pocket anyway. Given the cost of the scope I'm not sure that it's worth it. It would probably be more cost effective to send the 72ED back and buy something else , or to shorten the tube if it is easy enough to remove the focuser and re-fit.