Ricochet

My LS50/B600 focuses without any extension tubes with every eyepiece I've tried in it. Granulation and proms are visible if it is in focus. If it is not properly in focus then you lose details. Edit: having said that, focuser travel is rediculously short, and there isn't enough infocus for use with my 2x TeleXtender (plus eyepiece).

If it is described as f6+ and your scope is f5.9 I wouldn't worry about it as the difference will be so small as to not matter.

These days all eyepieces are universal, you don't have to stick to Celestron. There are three common sizes you might encounter: 0.985" - only found on old telescopes or with really, really, cheaply made modern scopes. 1.25" - Most modern eyepieces are this size, and this is the size your telescope takes. 2" - Required for long focal length, wide field of view eyepieces. Your telescope can't use these. With regards to selecting new eyepieces, the first thing that you should do is to get some experience using the ones you've got so that you can better understand the features that an eyepiece will have and what is important to you, for example the eye relief (distance your eye must be from the lens) and apparent field of view (how big the image circle appears when you are looking through the eyepiece). Once you have that knowledge you need to decide on what your budget is for a new eyepiece and what you want to observe with that eyepiece. For instance, if you want a finder eyepiece to maximise the true field of view that your telescope can deliver then you will want to be looking at something like a 32mm Plossl or a 24mm 68° eyepiece. If you want a good general purpose DSO eyepiece then you will want something that produces an exit pupil in the 2-2.5mm range, which with your f5 scope corresponds to a focal length of 10-12.5mm. For planetary viewing look for something that gives a 0.85-1mm exit pupil, so a 4-5mm eyepiece. Having found candidates that fit your requirements, search for reviews on those eyepieces look for reviews on them and feel free to post here for people to give advice on an eyepiece and/or alternatives.

Does the vendor use the word aperture or have you added that word? "f6" describes the focal ratio of the telescope or camera lens, not the aperture. I think the confusion is from having used camera lenses, which have a fixed focal length and an adjustable aperture. Adjusting the aperture also changes the focal ratio, as the focal ratio is focal length/aperture. For example if you have a 35mm camera lens with a 5mm aperture, then you have a focal ratio of f7. If you then increase the aperture to 7mm the focal ratio becomes f5, so the aperture has increased, but the focal ratio has decreased. So while the focal ratio of the camera lens has changed, it has only changed indirectly, because what is actively changed is the aperture (measured in mm), even if the camera scales are only marked as the ratio to the focal length. With regards to eyepieces, if the phrase used is "works with telescopes f6 or above", it means telescopes with a "slower" focal ratio, that is f7,8,9 etc. The focal ratio describes the angle of light coming from the objective that the eyepiece must correct so that your eye can generate an image. The steeper that cone of light is, the more difficult it is to correct. That means that an eyepiece which is suitable for f5 telescopes will always also be suitable for f10 telescopes, but an eyepiece suitable for f10 telescopes may not be suitable for f5 telescopes.

Maybe you were lucky and it was pretty well centred under the focuser from the factory. All I can say is in that the photos you've uploaded it looks out now. If you don't already have a Cheshire an alternative that might be easier to use in a fast scope would be the Concenter .

If you look into the focuser with the open end of the tube on the left and the primary to the right, your secondsry mirror is way too high. You need a cheshire/sight tube to correct this and align it with the focuser, you can't do it with a laser. Once you have that step done you can align the secondary with the primary. Again the Cheshire/sight tube is the best option, but you can use your laser if you have accurately collimated your laser first. For the final step of aligning the primary use either a Cheshire or a barlowed laser. Don't use a laser by itself as any error in the previous step will result in double the error in this step.

Only in the event that you have an eyepiece that needs more outward travel than your focuser has and you need to work out what size extension tube to buy. In normal use you want the eyepiece to be held securely.

Don't use the Baader fluid to clean the mirrors, unless you have bought enough of the stuff to submerge the mirrors in it and let it soak. With regards to the scratch, do you have a photo of it? If it is scattering a lot of light I believe the best thing to do is to paint it black with a suitable paint pen.

If you go anywhere that is darker than your current location then you should see an improvement. The key is to be away from man made sources of light as much as is possible. If you are observing from an urban or suburban location then DSOs that are star clusters will be easier to observe than nebulae or galaxies.

That is an absolutely awful way to mount solar film. Where is the redundancy in case the tape comes loose when the sun heats the scope cover and therefore tape? In such a scenario the film would fall into the telescope and anyone observing would be instantly blinded. What is that crease in the bottom right corner? Is the tape even coming off in the photo that you've posted? Where is the protection against damage for the underside of the film when the telescope is not being used for solar observing as per the safety instructions supplied with the film? Where do you put the telescope cover when you are observing at night so that the solar film does not get damaged? As far as I am concerned you should never, ever, observe the sun using that method of affixing the film. The fact that you apparently also risk the eyesight of members of the public by allowing them to look through a telescope with a solar filter mounted in such a way, and are also suggesting it online for others to copy, is absolutely abhorrent. If you want to observe with the telescope stopped down to the small hole, then you should build a proper filter cell that fits over the lip on the outside of the cover and that can be securely fixed to the telescope. That cell can then be stored in a container to prevent damage whilst not in use.

Try astroboot. I would also query the seller in case they have the original part or there is some reason why it is not needed in this case. With respect to your focusing issue, point the telescope at the moon. If you stand back from the telescope while it is pointed at the moon you should see a small, bright doughnut shape in the centre of the 25mm eyepiece. Bring your eye to the eyepiece so that this doughnut expands and fills your vision. This is the point that your eye needs to be to see the image. As I don't know the eye relief of these eyepieces I suggest you do it without glasses. Once you have your eye in the correct position, turn the focuser knob and you should see that the doughnut shrinks in one direction. Keep turning the focuser in that direction until the moon comes in to focus. It is likely that you will need to rack the focuser outwards. If you reach the end of focuser travel without reaching focus, or the doughnut starting to shrink, try to carefully withdraw the eyepiece whilst looking through it. If this brings the moon into focus, or starts to shrink the doughnut, then you definitely need the extension/adaptor. With respect to your focuser, I think that this may not be the original focuser as the Skywatcher Skyliner is always sold with a black focuser as far as I am aware. Yours has a white focuser, as sold with the current "black diamond" Explorer and collapsible dobsonian ranges. I do not know why someone would replace a focuser with the exact same focuser in a different colour. The 150p is or was sold with a rack and pinion focuser, so perhaps some old examples of the 200p also had this focuser and it was replaced as the seller stated. In this case you need to apply the advice in my previous paragraph as the focal plane might be in a different position to the current model, and your first problem is that you have your eye nowhere near the right position to assess the focus.

I think that asking a question is also contributing. In the future other people may have similar questions and also find this thread. With regards to your two choices, between an 80mm f8 and a 90mm f5.5, I think the f8 will probably give more pleasing terrestrial views and would therefore be my choice. Hopefully the issues you saw with the previous example were a one off.

Did you agree to pay via Paypal before sending payment? Unless I know and trust the person I would always pay via Paypal (with fees) to ensure I had protection in the event that something goes wrong, and when I sell I always expect to pay fees to give the buyer those same rights. The moment that the money was refunded and the seller insisted on bank transfer you should have walked away. If there is an advert on ABS with no public photos for everyone to see, or they won't pay via Paypal, then I assume they are being dishonest. It may not always be the case, but resizing photos so that they can be uploaded to ABS and setting up a Paypal account so that things can be paid for safely are easy things to do, and the absolute minimum that someone wanting to sell an item should be prepared to do. Given that the ABS seller started off by advertising the tripod with a Celestron wedge, it should have been quite obvious to them that the tripod they had might also be a Celestron tripod, rather than an EQ6, and they have no excuse for not refunding the money.

Don't worry about buying more eyepieces before you have had a chance to use the telescope for a couple of sessions with the supplied eyepieces. You are unlikely to need a 3x barlow, but a 2x may be useful depending on which eyepieces you buy. The X-cell LX range will work well in the shorter focal lengths, say the 12mm and below. You can buy better eyepieces, but whether you can buy better eyhyepieces for your budget may be a different matter. If you give us a budget to work with we can give better advice. Whether or not you need glasses will probably also impact your choices.

Is this issue during the day or at night? If it is during the day, the "problem" is likely to be seeing the central obstruction in the 4mm exit pupil when your own pupils are not dilated to 4mm.

You also mention M5 screws, perhaps those would foul on the recesses. Are you sure you need to rotate the holder? The spider arms are in line with the focuser, so the recesses should ensure that the secondary is orientated towards the focuser properly. I suppose if the focuser axis isn't aligned with the spider arms you might need to rotate the secondary. I actually had that sort of issue with mine as the tube isn't quite circular. I shimmed the focuser with a couple of washers under the bottom screw fixings to get a better alignment.

This is now sold as the Skywatcher Startravel 80 (ST80). Assuming that the telescope and mount is in good condition, £50 is a good price and you should easily be able to get your £50 back should you decide to sell it in the future. This would make it an ideal test scope to see if you you enjoy astronomy and what you need from a scope. As far as I can see, all the parts are there, just check that the diagonal can be clamped in the focuser properly if/when you go to get it. With regards to the telescope, it is an 80mm f5 achromatic refractor. 80mm is probably about as small an aperture as you want to go and so this is the sort of thing that is generally bought as a first scope, and then kept as a "grab and go" scope when there is a quick break in the clouds and you don't want to go to the effort of getting a bigger scope out. It would also make a decent travel scope, although perhaps on a mount that doesn't require counterweights. As the ST80 is a fast achromat, there will be blue halos around brighter objects, and so it is going to be best suited for low magnification star field sweeping, rather than high powered lunar and planetary views. Is this the review you mean Geoff? ST80 Review

The 8" doesn't have the metal plate. Why they are different I don't know. From memory the y shaped part of the secondary holder has three recesses that the screws press into. I wonder if perhaps the swarf is from where the recesses were originally drilled out, rather than the screws cutting into the holder.

It's nothing to do with your vision compared to someone else's . The brightness of extended objects increases with exit pupil so the bigger the exit pupil, the brighter the sky background. This results in a loss of contrast between stars and the background sky. You've got a 24mm, so you can see the brightness of the sky in that. A 35mm will have a sky brightness roughly double that of the 24mm, which due to the way your eye works will appear as one "step" brighter so you can use that gauge whether you think a 35mm will be too bright. Your 11mm is roughly a quarter as bright as the 24mm, so two steps darker to your eye.

Was it the 8" f6 or 10" f5 you bought? A 35mm eyepiece would give an exit pupil of either 5.8mm or 7mm, which will likely give you a washed out background under light polluted skies.

Thanks to everyone who commented on this thread. In the end I went for the feathertouch focuser and a double stack unit while it is in the sale. Having looked through it this afternoon I am blown away by the improvement the double stack makes to the visuals and would immediately recommend getting it to anyone still considering it. The focuser is also a massive improvement with a lovely silky movement. Making the swap is very easy, the only tool required is a 1.5mm hex key so that you can rotate the focuser to your preferred position once it is screwed on.

If I've found the right screws in my astro drawer, the 1st generation run of the Bresser 8" dob used M4x25mm round head screws for the secondary collimation bolts. I made my own thumbscrews from something like M4x40mm screws and some spare tyre valve caps. However, I've since had the secondary/spider replaced and I've not bothered changing them on that. You can do the screws up quite tightly with a screwdriver so that once it's in the right place the secondary doesn't move and recollimation isn't necessary.

No, not exactly the same. Look again: Left is with mirror clips, right is without. The clips don't create spikes, they prevent them in some areas (but this is more complex than the standard 120 degree shadows normally seen). This is exactly what you need to do. I think everyone should do this, no matter the make or model being used. Even if the mirror arrives in perfect condition, over time the coatings will degrade and the edge of the coating will be the first place to go, creating spikes like this. A few mm off the aperture is a small loss compared to the tighter star images. Unfortunately, if changing the secondary changes the spikes, you may also need to mask the secondary.

It is quite common but not universal. Some people don't get on with binoviewers, some love them, but you won't know which camp you fall in to until you try it. Binoviewing for DSO viewing is quite uncommon as the combinations required for focus tend to limit FoV and exit pupil.

Short term I would get something cheapish like a 7mm Nirvana or X-Cel LX, and/or barlow the longer focal lengths you already have. Long term I would find a binoviewer and barlow/gpc combination that will come to focus in your scope. Once you have that you can calculate the actual magnification the system is providing and figure out the focal lengths you will need with that.