Louis D

Afocal projection always has the negative aspect of capturing any image artifacts introduced by the eyepiece and the camera's taking lens. For the 36mm HA, that would include pincushion distortion and chromatic smearing at the edge: If you can live with these imperfections, it's not a terrible way to quickly capture images. I captured the following moon image afocally through a 14mm Pentax XL with an Olympus C4000 camera 16 years ago:

The image circle of many telescopes is simply not large enough to cover a full frame 35mm DSLR sensor. If you were to draw the bounding box for your cropped sensor on the above image, it would probably show a bit of vignetting in the corners. A focal reducer will simply squeeze the image circle down even smaller, so you would likely see vignetting on your 700D. You might want to try a Barlow since it diverges the light cone, spreading it out over a larger image circle.

See the opening of Idiocracy for where humanity is likely headed. 🤣

I fail to see how these keep your fingertips warm in sub-zero F temps unless you keep your hands in a hand warmer waist pouch while observing. I'm more partial to ice fishing gloves with flip-up mitten covers.

Of course, I'm more partial to the Big Bang Burger Bar at the other end of the universe: Than I am to Milliways:

Perhaps @FLO could source similar caps for the UK market? These replacement cap requests come up quite often on SGL.

I figure it's so far in the future, that humans probably won't even be around anyway, so no worries here. I'm more concerned about paying for retirement in a few years. 😉

My understanding is that locally (e.g., within gravity groups), gravity can overcome the general expansion of space-time at this point in the age of the universe. If it continues to accelerate its expansion, this would no longer be true at some point in the distant future.

It couldn't be 2 millions years since the Andromeda galaxy is about 2.537 million light years away, so it would have to move faster than the speed of light to get here in 2 million years.

That is going to depend on how many floaters you have in your observing eye. I find that exit pupil to be right at the limit for my eyes. Below that, I have to keep flicking my eye to move the floaters out of the way for a second or so to see something clearly. There are folks using Vixen HR eyepieces down to 1.6mm in APO refractors, so it really depends on the person and the scope how low you can go on exit pupil.

On your side of the pond, you could try Zeiss spheres.

My rule of thumb is, if I can move a star around in the field, and it gets noticeably worse in some areas, I'll check the eyepiece for eye lens smudges. If they exist, I'll clean it the next day, but never in the field. It's too easy to grind bits of grit across the lens when outdoors. If I can't notice any difference across the field of view, then I'm usually good with my eyepieces. I did do a cleaning day last year of all my eyepieces because I had a bit of free time. I hadn't done it in years. There was only a thin, even film on most of them that probably had no effect on the image anyway. This is all in relation to the eye lens. I don't recall ever cleaning a field lens (bottom lens) on any eyepiece, let alone disassembling them for interior lenses. Alright, I did take apart a 40 year old orthoscopic eyepiece that was really cruddy that I had bought used for cheap, but that's a different situation.

The Caldwell catalog is another good resource for showpiece objects missed by Messier.

Quick initial impressions and first light on CN here and here by member LDW47. There are also more user impressions further down by LDW47.

Yes, the eye lens on the Pentax XLs are 30mm in diameter versus 35mm for the XWs. The XW eye cup's hole must necessarily be larger to allow the entire eye lens to be seen. I think it's pretty clear from this image I took that the 3.5mm XW on the far left has a larger eye cup hole than does the 5.2mm XL second from the right. The XL cup's conical taper also appears to be noticeably taller as well.

I would start with the SV171 and see if you like using a zoom eyepiece at all. Some people just don't care for them on a day to day basis. I mainly use a pair of Celestron/Olivon Regal zooms in my binoviewer because it's such a pain to change two eyepieces to change powers and to make sure they aren't tipped in their holders causing merging issues. In general, I prefer monoviewing DSOs with premium wide field eyepieces. Planets and the full moon demand binoviewers, though. I just see so much more detail with two eyes with them.

The only other galaxy (core) I found to be super easy from Bortle 6+ skies besides M31 was NGC253. However, I don't know if gets high enough for UK observers to see.

I have a 20mm TPO spacer ring from OPT on my 12mm Nagler. It doesn't thread on all the way, so it's more like 22mm or so of extension. As a result, I've got 7mm of gap between the bottom of the 2" extension and the bottom of the 1.25" barrel. I just found a snapshot of this eyepiece that I had forgotten about:

I think this is why EEVA is gaining popularity.

If they were exactly the same length, would 2" filters safely clear the 1.25" barrel? It would be mighty close.

I bought a couple of parfocalizing rings, but decided not to use them when I saw the sharp points on the set/grub screws. I didn't want to ruin the resale value on my eyepieces by digging divots into the chrome on the lower barrels. That, and they had to be secured into the lower taper of the safety undercut which wasn't going to be very secure. Instead, I used rubber O-rings to bring my 12mm Nagler T4 into parfocalness with the rest of my eyepieces that focus at the shoulder. I think I used a stack of five 4mm thick ones with a 50mm inner diameter. It works well enough that I need only a small focuser adjustment now to bring it into focus relative to my ES, Baader, and Pentax eyepieces.

I have the Arcturus branded one which I believe is sold as OVL in the UK. The same base unit is sold with different eyepiece holders by Williams Optical (WO). Most folks prefer the collet lock (OVL) over the set screw/compression ring (WO) versions. There are other brandings out there. Do a search and check back on SGL for user opinions on whatever you find. There are of course higher end binoviewers, and they have larger prisms to allow for wider views, better eyepiece holders, greater attachment flexibility, and system accessories such as power switches. However, for starting out, the basic models with smaller prisms are fine performers for planetary viewing. You'll need to budget for a pair of decent 50 to 60 degree eyepieces and possibly for a Barlow nosepiece (or dedicated GPC/OCS) to reach focus if the included one doesn't work for you.

I would avoid that pedestal mount unless it can be bolted to the ground. It's going to tip over at some point unless there's a 100+ pound iron or lead weight at the bottom. Personally, I would start out observing and not worry about astrophotography for a while. Learn the sky and enjoy finding objects.

70mm achromatic refractors don't have much light gathering power and suffer from chromatic aberrations. So, they tend to be a bit disappointing to look through. That, and that mount isn't all that great. It tends to be wobbly and difficult to track objects with. That's not to say all 70mm refractors aren't great. I love my 72mm ED refractor for wide field views. Its short focal length and low chromatic error make viewing large swaths of the sky very enjoyable. However, I have it mounted on a very capable alt-az mount that I purchased separately.

I used one of those 76 Dobs at a star party. It's pretty close to impossible to aim it at a target while perched on a table due to it super short length. I've been observing long enough that I was able to aim it by "shooting from the hip" so to speak. However, I wouldn't expect a beginner to be able to do this. In the central 25% of the field, the view of Jupiter was enough to see banding once it was on target. It's not a great view since it uses a spherical mirror instead of a parabolic mirror. As alluded to above, these show up in thrift stores for about $10 to $20 after Christmas because they tend to be underwhelming. That's where the advanced observer at the star party had picked up his two examples. He puts them out on a low table for kids to try and use. However, none of kids or their parents could get anything in the field of view until I came along. They were astounded I could get them to work when they had had no luck with them.