Mandy D

All that the focuser does is move the eyepiece back and forth from the objective to obtain focus. Putting a diagonal after the focuser does the same thing adding it's extra light path length to the focuser, so yes it will have this effect.

@PeterStudz Alice has asked a very interesting question, there. I'd like to take a stab at answering that. As you know nebulae are dust and gas clouds, so very diffuse and (ahem!) nebulous. If we image these things from Earth in purely visual light without any particular emphasis on certain wavelengths, I guess that might be close to reality. So as we approach the nebula, such that it subtends to the naked eye the same angle it did to our telescope back on Earth, it would look very similar, but with a more 3 dimensional appearance due to the eye having a shorter focal length. Remember, from photography, long focal lengths compress the field, short ones expand it - I'm not talking depth of focus here, but the appearance of depth, as in far things looking even smaller and further away in wide angle lenses. The other thing that will happen is something anyone who has flown on an aeroplane will be familiar with. Clouds that look like sheep from the ground become more diffuse and nebulous like a fog as you approach them and eventually fly through them. So, will see a foggier view with less apparent detail as we get very close. This is just my first thoughts on the topic, so I may well be wrong, but it makes sense to me and I hope it helps Alice.

@Chriske Thank you for the further explanation. Are the plane mirror and screen both tilted at a slight angle to the spherical mirror? I guess focal length is rarely, if ever, critical as long as it can be measured and known where necessary. I look forward to seeing more about this project as it progresses.

@Epick Crom How wonderful! It is so nice when you can get others interested in actually looking through the eyepiece, especially younger family members. I have a small gap in the tree line exactly where the Sun set last night, but my 200P on it's original Dobsonian mount can't see over the garden wall, so I missed it. I can't wait for my Skytee mount to come back so I can see such low things. If the sky is clear tonight (unlikely) I might try moving it to another location away from home. I need an image of Mercury (other than in transit) to complete my family portrait of the planets.

@LDW1 petroleum jelly is oil-based, unless you are using an alternative that I am not aware of. It also well known that it attacks latex rubber. For PTFE it will be fine, as will most chemicals, as PTFE is pretty much chemically inert and resistant to chemical attack.

@Chriske Very interesting. What would be the optical arrangement of this telescope? A quick sketch might help, if you don't mind. I presume the ultra long focal length is to obtain a decent size image for viewing on your screen. I get 10.93 mm diameter at 1200 mm focal length, so, I guess you will be around 500 mm with that enormous focal length (55 m), which explains the screen size and choice of focal length. I'm sure you have done the number crunching for this and got the correct answer (so, I may wrong), but I think your screen seems a bit on the small size. I would certainly be interested in knowing more about this project.

Thank you. Yes, I am just starting to realise this after grabbing this image and now looking for more opportunities.

Nice! Can I ask what your exposure details were?

I have to wonder if he actually did get around to drinking the Domestos in the toilets.

@Richard N Almost certainly PTFE on mine. It is white with a very low coefficient of friction and feels soft enough. It certainly slides well on my AZ baseboard. Have you owned yours from new? Have a look at the photo which shows one of the pads stapled in place and the centre washer.

No, actually I am not. I haven't actually examined any since I first took delivery of my 250PX several years ago. PTFE is really quite soft and flakes easily, but I now think I recall the pads being hard. I'm sure others have said they are PTFE, though. If I can find the right spanners, I'll check mine.

@Richard N The az bearing on a Skywatcher dob should not need lubricating, ever. It runs on PTFE ("Teflon" ®) pads. Have you checked how tight the central bolt is in the Dob base? If that is too tight, the azimuth motion will stick. Slacken it off until it works OK and remove the lubricant you have applied.

@PeterStudz I had Jupiter near the Moon in daylight recently, shortly before sunrise and got Ganymede and Io in an image. Callisto was far too faint and Europa was playing hide and seek behind the planet. It really is amazing what can be seen during daylight hours.

Dome head socket ("Allen") or Torx screws would be my preference for replacements, but not in stainless steel as it reacts with aluminium.

Wow!

@BrendanC I've just checked on mine and it measures up as 4 mm with a thread pitch of 0.70, so it should be a standard M4. Length is 6 mm and it is a pozi-pan head. If the new one does not screw in easily, then it is probably the wrong thread.

The Moon and Jupiter with it's Gallilean moons. If they are prepared to spend a few minutes at the scope they should see that the moons are moving in relation to each other and the planet. Our own Moon shows an amazing amount of detail even in small telescopes.

Yikes! We really should stop complaining about the weather in Britain! I do have some photos of the Sun, taken in Derbyshire, with a Saharan dust cloud covering it that was pretty spectacular.

Read the terms and conditions carefully before deciding if the courier will be fully liable. Usually, you would need to take out separate insurance to fully cover the high value of light equipment such as telescopes. RHA compensation rates are something like £1.50 per kg. Yes, some will offer extended cover, but I have never seen one offering full value, certainly not as standard. Yes, then there are baggage handlers! Have you ever been inside a parcel hub? I had cause to vist DHL's hub at East Midlands Airport. There were heavy parcels being thrown from the backs of vans, aimed at the conveyor belt, missing it entirely, then being picked up to be thrown at it again; rinse and repeat. Exactly the same process as used by airline baggage handlers. These people appear to be accountable to no-one. Your only safe plan is to package items to survive this type of handling. But, beware, if you over-package, you could fall foul of their terms and conditions and have your claim rejected. UPS require that all parcels are packaged in brand new double walled cartons and secured only with Kraft tape. Because one of our packages used the "wrong" but much stronger glass reinforced tape, ample high density extruded polystyrene foam and was packaged in a number of previously used cartons, the claim was rejected. Also, they will often only pay out on the actual weight of the part that is damaged. Further, you cannot claim for damage to the packing case or carton. That, apparently, is their's to wreck as they see fit.

Just to throw yet another option into the mix, I use my 200P on a Skytee 2 mount on the standard 1.75" tripod and find it works quite well for lunar, solar and planetary. I think you can now buy the Skytee 2 and tripod as a package for £399. Edit: You will need to buy tube rings and a vixen dovetail, too. If you fit the rings in the right position and orient the dovetail so that the focuser is rotated down 45° from it's original position you can still fit the scope on the Dobsonian mount if you ever wish to. I use mine as a convenient stand for storing the OTA. I recommend upgrading the saddles that are supplied with the mount, too.

The focuser is at an angle to horizontal for convenience in viewing. You would have to bend to some uncomfortable angles if it were parallel to the ground, so instead it is rotated about 45° to the horizontal. Why it is on one side and not the other, I guess is a judgement call or maybe more convenient for right handed people. I can see no particular reason for that. Incidentally, when my 200P OTA is mounted on a Skytee mount on a tripod, I have the focuser parallel to the ground, as it is sat so much higher than when it is Dobsonian mounted.

I totally agree. But, do large Newts never get delivered to the customer by a carrier? Do they not go through hubs and get thrown around and dropped off conveyors? Yet by some miracle most arrive in one piece and undamaged. I suspect that the packaging may have something to do with this, as they tend to use substantial chunks of shaped polystyrene and all my new scopes have arrived packed in two double-walled corrugated cardboard cartons. It must surely be possible to pack them to survive most of this type of treatment. When I transported my 250PX to France in the back of my Land Rover, a customs official lifted one end of the box it was packed in and dropped it from a good height!! I cannot repeat my words to him in here, but I was very, very angry. Amazingly, it did not even affect the collimation. It was in it's original packaging. Having said all of this, I have to stress that I am not disagreeing with you and I would definitely not want to hand any large telescope over to baggage handlers, no matter how well packed it was. I've seen what they do in parcel hubs and it is not nice. If the OP is serious about doing things this way, I would suggest talking to a specialist flight case manufacturer. This is who I use: https://theflightcasecompany.com/ They have experience of making cases for large telescopes.

It looks to me like the planet is very low in the sky. You have some colour fringing there, which is likely due to atmospheric dispersion (red at bottom, blue at top). You are also over-exposed. Digicam control allows remote focusing and is a free download. https://digicamcontrol.com/

Yes, even when you know where it is, it seems to take a while to appear.

I'm a bit late posting this, but I was going through my archives and found this photo of the total lunar eclipse from December 2010. The Moon was still clearly vibible in the sky to the naked eye, but my point and shoot camera didn't appear to pick it up. However, a fresh look at the image on a modern LCD monitor shows it quite clearly. I've also enhanced the photo in GIMP to attempt to make it that bit clearer. The Moon is above the rock, between the two bands of faint cloud and appears as a faint white disc. As best I can work it out, the photo was taken at about 07:50. The temperature measured by the car was -12 °C. We spent 45 minutes up there. This was the first total lunar eclipse I ever photographed. You may have to zoom in to spot the Moon.