Ricochet

What sort of budget are you thinking of? If you are looking for second hand equipment then the best place to look is the classifieds section on this website. Alternative places to buy second hand directly from other astronomers are Astrobuysell , ebay and some Facebook groups, but you will have to be more careful with those places. There are also a few of the established astro retailers who have started dealing in second hand equipment, but you will pay higher prices for the security of buying from a business.

In my experience a neodymium filter is absolutely useless on DSOs but the filter to use for lunar and planetary viewing. The only light pollution filter I have used that is useful on DSOs is the Astronomik CLS, but this will probably become less effective as LED lights become more common. There is a new (ish) IDAS light pollution filter designed for use under LED lighting that might be useful, even though it is targeted more at photographic rather than visual use.

No chance. The type of thing you describe is usually caused by water vapour. The possibilities that I would look at are: Observing when it looks clear but there is actually a layer of high cloud and/or general water vapour in the atmosphere. (Judging from clear outside this will be the case on 3/7 days this week) Dew forming on the eyepiece Poor coatings on a cheap eyepiece A low quality filter Internal reflections from the side wall of an extension tube/barlow/eyepiece Light scatter from the mirror edge

A 3X barlow is unlikely to be of much use in such a long focal length scope. A 2x option, such as the Explore Scientific 2x Focal Extender is a good choice, but it depends what your budget is. However, given that you only just got the telescope I would start by just using the eyepieces that came with it for a while before looking at other eyepiece options rather than a barlow. More magnification is not always better and many new users try to push beyond the limits that either their scope or atmospheric conditions allow. You're probably not going to need anything shorter than about 5mm with that scope and for DSO viewing an eyepiece around 10-12mm is probably going to be the most useful, as well as longer focal lengths for objects that require a wider field of view and/or filtered nebulae. To give suggestions we really need to have an idea of budget and whether you need to observe wearing glasses. You haven't mentioned collimation tools, but I would suggest investing in a good quality Cheshire/sight tube and learning how to use it.

Nice one John. The focuser baseplate has 4 little hex screws around the perimeter (2x 1.5mm and 2x 2mm I think). If you loosen those off you can rotate the focuser 45° so that it is in a better position no matter the altitude you're using it at. Also, I always use those big round holes in the base as handles.

I think your most expensive eyepiece should probably be the one you use the most, so I would start with the 16mm.

You want to get it so that everything is circular and everything except the secondary shadow is centred under the crosshairs. I would give it another go tomorrow and see if you can improve.

Yes, it is the difference between the mirror temperature and the air temperature that causes the problems. I think a fan should work both ways, in that when the air is warmer it will help warm the mirror and when the air is colder it will help cool the mirror. Perhaps you can get better results simply by not using the ac in the car on your drive to the observing site (if that is bearable for any people in the car).

I believe that a general rule of thumb is not to clean a mirror for a year after it is (re)coated to allow the layers to fully harden, but after that it is relatively safe to do. With regards to the amount of dirt, that mirror didn't have enough to necessarily require it, but where the dirt is organic in nature, it is better to clean it so that it does not eat into the mirror coatings. The worst dirt is a finger print, which is most likely to get on the mirror immediately after you have finished cleaning it and necessitates starting the cleaning process again.

Adjust the secondary to get the doughnut under the crosshairs. Once this is done adjust the primary to put the centre spot in the middle of the doughnut. I've just seen you list your location as Arabia. Given this, planet altitude will be less of an issue but I believe that cooling will be more of an issue. A telescope with a larger, thicker mirror takes longer to cool and your location may be prone to such rapid temperature drop that the mirror can never catch up. I would be inclined to fit a fan behind the primary to help speed up cooling. You should experiment to determine whether you get better performance with the fan still running or turned off once observing, but having it running while the mirror is out to cool should help. Having the telescope outside in the shade for as long as possible before an observing session will also help as you have found. It is related to the aperture of the telescope. A 250p is almost 2X the diameter of a 130p so the tube of air you observe through is almost 4x as large. You need this larger area of air to be stable in order to not see turbulence. The 250p also has a resolution almost twice that of the 130p so you can also see turbulence that is half the size of the turbulence that the 130p can see.

It is quite difficult to take a photo through a Cheshire but everything except for the shadow of the secondary should be centred under the crosshairs. In your photos it appears that this is not the case. You also don't have the focuser and/or Cheshire far enough out to see if the secondary mirror is centred under the focuser. However, none of this will prevent you from focusing the telescope. Focusing is simply a matter of having the eyepiece the correct distance out from the telescope. With respect to the planets, the low altitude will mean the atmosphere will often defocus the image, especially if you are observing over houses etc. I suggest you try focusing a high star. If you can focus the star then you have the correct adapters and extensions in your focuser and will also be able to focus the planets if the atmosphere allows. If you can focus a star but not a planet then consider more carefully what you are observing over and if changing the positioning of your telescope or the time that you observe will give you more favourable conditions.

I use a Telrad on the far side of a RACI finder with my dob. It is a bit inconvenient to look around the RACI but that is the preferable set up so that the RACI is ideally positioned for use while sat at the focuser. A Rigel has a significantly smaller footprint and so could probably go at the top of the OTA without needing to worry about it clashing with the positions of the focuser and finder.

If you can afford it, I would recommend the 24mm ES 68° to maximise the field of view a 1.25" eyepiece can provide.

Having looked through one, I'd say it is a negative only design 😆.

Probably hairs/fibres on your eyepiece lenses. The 10mm BCO is very good and the Vixen barlow will also be good. I don't think there will really be anything to gain optically by changing the barlow or by buying any of the eyepieces in your price range. If you were to switch to the SLV you would gain eye relief which should be more comfortable and might help your observing. The atmosphere really is the limiting factor this year so you will probably be best off not duplicating a focal length that is covered by your existing eyepiece and barlow. Given that you effectively have a 10 and a 5mm, a 7mm (or 14mm) would split them nicely.

What sort of budget do you have in mind for the telescope? Would you prefer a manual telescope, one that tracks objects once you have located them, or one that finds and tracks objects? I wouldn't worry too much about getting a telescope that advertises being able to fit your phone to it. There are only a couple of bright objects that this will work for and adapters can be bought separately. Generally, the telescopes that include them are low end.

Yes, I read about issues with specks of paint falling on internal lenses. All I can say is that the one 7mm I owned had no such issues and as an eyepiece I preferred it to the 8mm BST Starguider. The "Planetary" eyepieces are also BSTs and I see no reason why they would have better coatings than the generally more expensive Starguider line, which also shows the ghosting issues you remember from your previous "Skywatcher" branded Planetary so I suspect that still stands with the TS ones. I don't remember ghosting in the Xcel LX but it might also be there as my eye was less critical when I owned it.

I think it is suspected that the Celestron Xcel LX is the same as the Meade HD 60 of those are any cheaper. I'm not really sure why I sold my 7mm, someone got a bargain there.

When adjusting the angle of the secondary mirror you use the three outer screws and leave the centre one. You must unscrew one a touch and then screw one of the other two up. You should be able to see which way the mirror has moved. It is a case of trial and error to learn how to adjust the screws to get it to move in the way you want it to.

There are one or two lenses that act like a barlow, not a removable barlow. You should not remove them.

If it is for visual use I would recommend either the Dobsonian Skyliner 150p or the (shorter) Explorer 150p on an AZ4. Don't get an eq mount for visual.

You would use a clear filter when you have multiple filters in a filter wheel and don't want to have to refocus when switching to the "unfiltered" view. Imagers in particular would use this method.

Oh yes, of course. Look at the Newtonian light path diagram: The light from the primary makes a cone with the point at the focal point. On the outside of the focal point it crosses over and so everything will be flipped 180°. As before, what you are doing is not a star test. I don't know that being so far out of focus gives any useful information about your collimation.

It is no different to the view in the photos you took in the daytime, except that the inside of the telescope is illuminated by starlight rather than sunlight.

Definitely try to find somewhere you can see these scopes before you buy one. An 8" reflector on an eq mount is even bigger and more difficult to set up than the dob version in my book.