Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_lunar_close-ups.thumb.jpg.88a09e422111459fcea8be71befc7874.jpg

Ricochet

Advanced Members
  • Content count

    1,209
  • Joined

  • Last visited

Community Reputation

688 Excellent

2 Followers

About Ricochet

  • Rank
    Sub Dwarf

Profile Information

  • Location
    Hertfordshire

Recent Profile Visitors

2,449 profile views
  1. Ricochet

    What did the postman bring?

    Nice. It would be good to hear what you make of the 62° line once you've had a chance to test them. I don't think we've had many (any?) reports so far.
  2. Ricochet

    good lesnes for xt8 and filters?

    Svbony is a brand stamped on generic stiff coming straight from China. It is the same quality as all the other stuff coming out of the same factories and having more expensive brand names stamped on. With regards to colour filters you may or may not find a use for them. Some people like them but I think most tend to leave them in the case. With respect to those particular filters they are only threaded on one side so you can't stack them if desired.
  3. Ricochet

    First scope

    Astroboot links don't work in a way that we can see what item you are referring to. What does the description say? If you already bought something it is likely to have been removed from the site, but looking at the rest of the items on sale I'm not seeing any focusers suitable for a refractor.
  4. Ricochet

    Best eyepiece for saturn

    I think this is probably correct. Having recently looked at Jupiter through a 114/500 the best eyepiece was a 4mm. With the current low altitude anything more was too much. For your 114/1000 I would expect you would find the same issue once you get down to an 8mm (or the current 15mm+2X barlow). However, the corrector lenses in this type of telescope do not have a good reputation and it is possible even these suggested magnification levels will be too high for your scope.
  5. Ricochet

    First scope

    Each eyepiece will only show objects at one size. The focuser is just that, rather than a zoom function. The point of best focus is when an object is at its smallest. For magnification we can use Magnification = focal length (scope) / focal length (eyepiece) This means that an eyepiece with a smaller focal length will give a higher magnification. Let's say that you want to try going down to an exit pupil of 0.75mm. It is lower than the numbers I have above but your telescope is a refractor with a high focal ratio and small aperture so it might give nice views still. 13.3 x 0.75 = 9.975 so you buy a 10mm eyepiece. 800mm/10mm = 80x magnification. You should also be aware that the planets are very low in the sky over the next few years for us in the UK. This means we have to look through a lot of atmosphere which can really wash out details that are usually visible.
  6. Ricochet

    First scope

    From this we can calculate the focal ratio of your scope as 800/60= 13.33. This is useful when choosing eyepieces on the basis of exit pupil (the diameter of the circle of light that is projected above the eyepiece). Exit pupil = Focal Length (Eyepiece) / Focal Ratio We can then use the following exit pupil approximations: Maximum magnification for technically splitting double stars = 0.5mm Optimum planetary magnification = 0.85-1.0mm Maximum aesthetically pleasing magnification for objects visible as point sources (if they fit in the field of view) = 1mm Optimum magnification for unfiltered extended objects (if they fit into the field of view) = 2-3mm Lowest magnification without loss of light (subject to your eye and light pollution levels) = 5-7mm Your 12.5mm eyepiece will produce an exit pupil of 12.5/13.3 = 0.94mm so we can see that in this scope it falls into the planetary eyepiece category and is probably at the top end for viewing star clusters as well. With such a "slow" focal length refractor you may be able to use a smaller exit pupil on planets (definitely on the moon) than I have suggested so you may wish to find a slightly shorter eyepiece but I wouldn't push it too far as you are already near the limits that a small scope can handle. You might find it more useful to look only for one longer focal length eyepiece for wider views and then put the rest of your cash into a fund for your next scope. I assume those are the set that can be found on ebay for wildly varying prices. They're all the same so if you do choose to buy them go for the cheapest. I bought that set for my first scope and discovered they just have cheap plastic lenses. The 4mm and 6mm are in fact identical eyepieces aside from the number stamped on the top and not worth buying. The 12.5mm won't be as good as the one you've already got so that's not worth buying either. The 20mm is ok and might be worth spending a few of pounds on if you can get it separately for less than the set costs. I see that ENS Optical have an old Japanese 25mm that would be better than the one provided in the set. http://ensoptical.co.uk/circle-t-25mm-huygen-eyepiece-.965?search=0.965
  7. Ricochet

    First scope

    That does look like the smaller size. As it's a refractor you've got, what you could do would be to buy a 0.965"-1.25" diagonal which would allow you use 1.25" eyepieces. Astroboot have a few different options but there may also be other vendors who stock them. I can see your telescope has a 60mm objective but haven't found the focal length which you will need to know to calculate magnifications. This diameter is quite small and undoubtedly you will want a larger telescope in future but it should be enough for you to decide whether stargazing is for you.
  8. Ricochet

    First scope

    Check the barrel diameter of the eyepieces. If they are 1.25" you will be ok but if they are 0.965" you may have trouble sourcing decent eyepieces at a reasonable price.
  9. Tightened, otherwise you're just turning the mount rather than undoing it.
  10. I think you need to reconsider this idea. Telescopes are outdoor equipment. Leaving aside the issues you will have with the quality of the glass in those windows, thermal currents and an extremely restricted field of view, I'm not sure an equatorially mounted 200p will even fit in the gap under a window if it's a normal converted attic you've got. If you want to observe from inside the attic I would suggest just getting a pair of binoculars. At a push a small scope on an alt-az mount might be ok for low power views. Unfortunately, it doesn't work like normal photography. "Snapping what you're seeing" isn't really an option. You can hold a compact camera or smartphone up to the eyepiece to take a snap but this only works (poorly) for a few of the brightest objects. For everything else it is huge data capture sessions. The book "Making Every Photon Count" should be your first purchase if it is deep sky photography you are really after.
  11. I've had a couple of sessions to try to test out this eyepiece. At f6 the main issue that I see is field curvature. From half way between the centre and edge of field stars begin expanding into out of focus circles. Towards the edge they are large enough to see some sort of "clipping" on those circles, perhaps because the field exceeds the fully illuminated area or some additional aberration. Winding the focus in would correct the stars at the edge of field. The first time I attempted to test the eyepiece I was not expecting it to be clear and so had not taken the scope out to cool prior to observing. It had been a hot day that quickly turned to a cold night and unbeknown to me, one of the support bands holding the cooling fan had perished and so the fan was pulled off centre and not cooling the mirror evenly. This introduced a whole load of astigmatism which produced aberrations that seem to resemble your description. I have made a diagram showing the issues I could see at the edge of field. The left hand side shows the field curvature dominated effect (but the "clipping" might have appeared on the inside rather than outside, I can't quite remember) and the right hand side shows what happened to that field curvature when astigmatism was added on top of it. Apologies for the quality of my drawing. If you see star shapes as on the right hand side of my image I would suspect there is some astigmatism coming from the scope as well as any in the eyepiece. Perhaps a longer cool down period is required given the way the mirror is fixed to the plastic mirror cell.
  12. I see no evidence of a "central blockage" as you have drawn on your diagram in any of the photos. All I see are the shadows of the secondary mirror and the baffle through the primary mirror. I am confident that any SCT owner taking a photo through the visual back would produce a similar image. As before, you need to place a camera with no lens attached into the camera chamber and move it back and forth to find the focal point. At this point you will not see the shadows in the central area.
  13. Ricochet

    Show us your Frac

    That is a shame. It seems to me to be a bit of an oversight by Skywatcher not to make it easily compatible for RACI use.
  14. You would have no difficulty fitting either to the mount. However, I will have to leave it to others to advise which specific mount is sufficient for the 200p(ds).
  15. If you're wanting the 200p for visual use I think the dobsonian mounted version would be a much better option. If you're thinking of astrophotography then you'll want the pds version and a more stable mount than the eq5.
×

Important Information

By using this site, you agree to our Terms of Use.