Ricochet

The problem with a collimation cap is that it is really a tool for checking/adjusting the primary collimation when the primary is centre spotted. If a few pounds can be spent then short cheshires are available on eBay for less than £10 directly from China. Assuming that the primary is centre spotted, this would be a much more accurate tool to check collimation. If a collimation cap is all that is to hand then it is better than nothing, but it may be hard to judge the collimation accuracy using it, especially as in a fast scope the secondary shadow will be quite offset. With regards to an eyepiece to test, an 8mm Starguider and 2X barlow would do the trick, or an eyepiece from the "Planetary" line of eyepieces. The key here would be to buy something that has a negative element in the nose so that the light cone is narrowed by the time it gets to the main groups of lenses that form the image when that eyepiece is used without the barlow. A problem with collimation would move coma into the centre of the field of view, but I don't think that this would exclusively lead to the description of "fringing", which sounds like there are other issues in the eyepieces on top of the coma from the telescope.

The biggest problem I think there is with this approach is that we all have differing opinions. If a flowchart were to be produced, it would contain only the answer given by one or perhaps a select few to each question. Where a new user posts a query here, we can all give our differing opinions for the user to consider, and any advice would be tailored specifically for that user based on their responses as in conversation we may pick up o something that would be missed otherwise.

This is a good question. Focusing on something further away requires the focuser to be wound further in, which suggests that currently there is something holding the eyepiece too far out from the focuser.

Unfortunately, the telescope drawtube (the silver part you're pointing at) appears to be missing the eyepiece clamp that should be on the end of it. You would have to determine the measurements of the thread on the end of the drawtube and then see if you can find a 3rd party clamp available for that size. Once you have a clamp you could then look at getting a suitable diagonal and eyepieces. If possible, I would go back to whoever gave you the telescope to see if they can locate the missing parts (particularly the clamp, the rest are standard sizes and can be easily replaced). The exposed cog on the mount suggests you may be missing at least one motor. Does the controller allow you to move the mount at all? If not does it move smoothly by hand? If the mount does not move reasonably well or the telescope does not stay pointing at whatever you point it at you would also need to look for a new mount, plus tube rings and a dovetail bar to fit the telescope to the new mount. At this point I would suggest you would be better off buying a complete new telescope.

It would depend how badly the eyepieces perform and if the coma from the scope could be distinguished from the aberrations from the eyepiece. A proper star test would require a shorter focal length eyepiece than those supplied with the telescope.

I would suggest the opposite. The supplied eyepieces are of a design that is intended for very slow focal ratios, but the scope is extremely fast. Until the eyepieces have been excluded, there is no way to tell whether there is a fault with the telescope.

These three holes must have screws inside that you can adjust using an allen key. The big phillips screw in the centre pulls the secondary to the spider, the three outer screws push against it.

That doesn't surprise me. I suspect most of us have been hit by the recent supply issues.

Thanks, Louis. Great information for when the time comes to flatten a frac.

I'm just going to leave this here. https://www.firstlightoptics.com/binoviewers/baader-2-inch-1-7x-glasspathcorrector-with-integrated-coma-corrector-for-newtonian-telescopes.html 🙂

Ah, I was thinking you'd bought the hexafoc version and wondering how they had changed it for the paracorr not to fit. If you do go for the hexafoc version it takes up something like 31mm so there's a bit of a focus saving over the standard extension and clamp but I would think it would still protrude into the OTA a bit. You might also find it doesn't extend far enough outwards for use without the paracorr, but it doesn't sound like that would be an issue for you now.

Given that you want a telescope to see a particular star, perhaps it is best if you are able to identify this star for us so that we can suggest a telescope that should be able to pick it out. Did the company give an HD number for the star by any chance?

What part of the clicklock prevented the insertion of the paracorr? I can't think of anything on mine that would do that.If you mean some extension tube fitted between the clicklock and focuser, I think you could do away with that as with the paracorr you are almost at the inward limit of focuser travel.

Out of interest, how do you connect the flattener for use visually? Is it screwed to the nose of a 2" diagonal with extensions to get the correct distance? Do you have to have any form of adjustment on it to change that distance for eyepieces that have their focal planes at different heights?

The new, lightweight, "ps" scopes have fixed primary mirrors that in theory do not require user recollimation. If you find this is not the case the three screws would have to be loosened and you would have to manhandle the whole mirror cell/backplate to alter the angle of the primary.

When you are comparing the new ES eyepieces to the Starguiders how are you doing so? Are you making direct monoview comparisons or are you comparing the single ES to binoviewed Starguiders? If you are comparing to binoviewed Starguiders then which pair of binoviewers and barlows/gpcs you are using becomes important. As you've bought Starguider eyepieces you may have also bought the Starguider binoviewers to match. The presence of a pair of 8mm Starguiders suggests that you may be using the binoviewers without a barlow/gpc fitted to the nose, but whilst you can do this with an SCT, you shouldn't do this because moving the primary mirror so much to allow focus introduces spherical aberration which will ruin high power views. On the other hand, the two gpcs provided with the Starguider binoviewers are absolutely terrible and should be replaced with nosepieces from 3rd party barlows. If you are comparing the views in mono mode then it is also important to consider which focal lengths you are comparing. If you are comparing the 14mm ES to the 8mm BST then it is also important to consider the difference in both exit pupil and magnification. With the 8mm BST the exit pupil has been reduced to 0.8mm. On an extended object like the moon or planets this will reduce the brightness and it will also mean that diffraction is the limiting factor to optical clarity, which will apply to all 8mm eyepieces, not just the Starguider. With regards to magnification, the 14mm will give you about 140x, which is a magnification that can be used under UK skies pretty much any time, but the 8mm will give about 250x, which is well into the region where the seeing is going to be a limiting factor and prohibit use of an eyepiece on many occasions, again something that will happen with any 8mm eyepiece. Having said all that, I do now that the quality of the coatings on the Starguiders is not the best and the correction of the 18 and 25mm variants is not great either (but might be OK at f10, I think they're ok at f12), so I can see why you would want to upgrade. Given that the 14ES has an 82° AFoV and the 34MV has a 68° AFoV I would take a bit of time to consider if these wider views are part of what you're looking for in a new eyepiece, compared to the 60° of the Starguiders (a touch less for the 8mm I recall), the 50° of your Plossls and the 40° of the 40mm Plossl. If a wider apparent field is part of what you're after then you can immediately discount most of your list. I would also consider whether you are looking for an eyepiece to work as part of your monoview set or your binoview set. Personally, I pretty much exclusively use binoviewers for lunar and planetary, so I would be looking at longer focal length eyepieces to be used with a binoviewer that has a barlow/gpc on the nose. This does make simple designs like orthos more comfortable to use as the eye relief scales with focal length. I started with a mix of short (5-12mm) Starguiders and ES68 eyepieces before moving to Pentax XWs. Personally, I thought there was a bigger difference between the quality of the view between the XWs and the ES68s than the ES68 and Starguider, so there would still be some advantage in saving for a more expensive eyepiece if you so wish. If you're looking for a top tier monoview eyepiece then I think the XW is a better choice than the Delite because the UK (FLO) prices are about the same, the view in the inner 62° of the XW is pretty much indistinguishable from the Delite, plus you get an extra 8° around the edge, the eyecup design is better, and it is less prone to dew formation. If it is for binoviewers then the XW is just a bit too big in my experience and the slightly smaller Delite is a better choice (but not with the Starguider BVs, because the collet aligns with the undercut). Going back to your original list I would limit yourself to the eyepieces in the 9-11mm range. Anything shorter than that is probably too limited by atmosphere. Like you, I would put the SLV as a front runner, but have been put off by the reports of internal reflections and so have not actually tried one.

Which scope do you already have and what are you looking to achieve/gain with the upgraded scope compared to what you have? The ETX125 is an f15 Maksutov so is mostly a lunar/planetary scope, if that is your thing.

Assuming by mechanical you mean a manual, rather than goto, mount, I would be looking at the following alt-az options. You won't want to use an equatorial mount as that will rotate the eyepiece of a Newtonian and the SLT has the dovetail bolted directly to the tube so you cannot even rotate it in the tube rings to counteract this (unless you also invest in rings). Skywatcher AZ4 Skywatcher AZ5 Scopetech Zero The AZ5 and Zero mounts will also require the purchase of a separate tripod with 3/8" photo threads. A good quality Gitzo or Manfrotto carbon fibre tripod would be my choice for compactness in storage/transport, or a Berlebach wooden tripod if you want top dampening and don't need as much compactness. All of these are expensive though and the AZ4 is the most cost effective option.

On double stars. For planets it's about half of that before diffraction starts scrubbing detail from the image. In addition, the UK atmosphere will often limit you to 150-250x, which would be matched by eyepieces in the 8-4mm range.

The focuser is just that, a focuser. It is not for zooming in and out. Standard eyepieces give a single magnification when used with a particular telescope. To calculate the magnification that a telescope-eyepiece combination gives use the equation: Magnification = Telescope focal length / Eyepiece focal length Rather than buying a whole selection of eyepieces of different focal lengths some people prefer to use a zoom eyepiece. A relatively cheap and well thought of zoom is the Hyperflex 7.2-21.5mm, one of which FLO currently have on their offers page. This eyepiece should be noticeably better than the eyepieces supplied with your scope, but you would still need to pair it with a 2-3x barlow of your choice.

The extra depth will allow you to store eyepieces vertically, so you can get more in than if you were to lay them on their side, so it is actually quite a good idea.

Yes, it is really not something to be overly worried about. It might take you a long time the first time you try it, but with a bit of practice it becomes quite easy. An f8 Newtonian is also quite tolerant with regards to collimation. I would advise you to buy a good quality cheshire eyepiece, and to avoid laser collimators (but you can do barlowed laser collimation for the primary if you like). With regards to DSOs, a bigger aperture collects more light so you can see fainter stars and magnify objects more, but the downside is more weight and more cost, and we all have to draw the line somewhere. An "APO" is an apochromat, a very expensive, optically well corrected refractor that doesn't have chromatic aberration (or rather, it is so small that you don't see it). The APO killer term refers to the idea that the telescope in question produces high contrast images that are similar to these much more expensive scopes. Visual 4" APOs that have become quite fashionable on this forum can be found here and a 6" APO from the same manufacturer can be found here.

I've got one of those and use the nosepiece with my binoviewers (not with Celestron branding, but they must all come out of the same factory), it's actually optically quite good. It would be worth trying it with the zoom to see how it works (if you haven't ordered another barlow). The problem could easily be the supplied 10mm eyepiece. The filters worth getting are UHC and OIII for nebulae (Astronomik or Televue ones), and a Neodymium filter for lunar and planetary (the Baader is the best, but the cheap Chinese one is also good). The tubes for keeping eyepieces in are usually called bolt cases. They're a bit fiddly if you have loads of eyepieces so most of us tend to keep out (ever expanding) eyepieces in a foam filled eyepiece case, typically a relatively cheap flight case. There is a very long running thread you may want to have a look at:

No worries, you have bought some very nice binoculars for someone who is new to the hobby. I think they would be the only pair of 10x50 binoculars you may ever need for astronomy.

Which barlow do you have? I have found that it is best to use barlows only to achieve high magnification viewing, rather than trying to add intermediate focal lengths between eyepieces. That way when you are using the barlow you put it in the focuser once and just change eyepieces, rather than continually swapping both the barlow and eyepieces.