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DevonSkies

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Everything posted by DevonSkies

  1. Good idea, I might try something like that. Also a good point about the aperture mask for moon and planets. I've found it virtually eliminates CA, but it does cause some loss of resolution. I forgot to add that I have also tried the Baader Contrast Booster filter, which is supposed to be the most aggressive of the CA-reducing filters. Although it did noticeably reduce the CA, it left a yellow cast which I found unpleasant and also noticeably reduced the sharpness of the view at high magnification. In the end I decided I preferred the unfiltered view! At some point I will probably buy a dedicated grab-n-go for lunar/planetary work (maybe a Mak or an f/10-ish refractor).
  2. mmmm.... 150mm f/8... now there's a thought! Not sure I could justify it alongside the 10" Dob though!
  3. I have been using a Skywatcher Startravel 102 for about a month now as a grab-and-go scope. I also intend to use it as a travel scope for holidays, but I've yet to try it in that capacity. So I thought I'd record some of my thoughts about this scope. Initially I purchased the ST102 with an AZ3 alt-azimuth mount, but I quickly found I didn't get on with the AZ3. On the plus side, it is very compact and lightweight and would make an excellent travel mount. However, I found the friction bolt arrangement for setting the altitude tension to be unreliable, and the mount was difficult to use near zenith. So, I changed the mount to a Vixen Porta II, which is much more comfortable to use. The Porta II tripod does seem to vibrate a bit more than the AZ3 though (especially on concrete), so maybe I will change the legs for something more substantial one day. Onto the telescope itself. The optical tube feels very solid and substantial. There is a large dew shield fitted, which is held on with a simple push fitting held in place by a felt band. Removing the dew shield reduces the OTA length significantly, but unfortunately the supplied lens cap won't fit over the front cell without the dew shield in place. This is a pity, as removing the dew shield would make the scope very compact for travel. The 102mm doublet objective has a blueish-looking coating, that seems evenly applied. The OTA assembly is supplied with decent tube rings and a dovetail. If you buy the scope in a kit with the AZ3 mount it comes without a dovetail, and the tube rings bolt straight onto the mount. The focuser felt quite smooth but a little tight straight out of the box. Initially there was no play in the focuser and the drawtube was well aligned. However, the focuser does prove to be a weak point on these scopes and I will return to this later. Now on to the important bit - performance! The OTA came supplied with the usual 25mm and 10mm MA eyepieces. The 25mm is quite a good budget eyepiece, but the 10mm could be better. However, since I already have a set of reasonably good eyepieces I put the supplied EPs to one side. Also supplied with the OTA and AZ3 kits is a 45-degree erecting prism. This is useful for terrestrial observation, but not really of sufficient quality for astronomical work (although it is OK at low magnifications). I replaced this with the excellent Revelation 2" Quartz Dielectric diagonal. This scope excels at wide-field views of open clusters and brighter DSOs. With a 25mm X-Cel LX eyepiece the whole of the Pleiades can fit in the field of view, which is a stunning sight. I also have a 32mm Panaview 2" eyepiece, which offers a whopping 4.4 degree field of view, framing the Pleiades beautifully within the surrounding sky. Under a dark sky the view is quite breathtaking. Other open clusters such as the Beehive also look superb with such a wide field. Best of all, this scope gives me the best view I've had of the Double Cluster in Perseus, with both parts of the cluster beautifully framed within the FOV. Large DSOs are also a strong point for this scope. M31 (Andromeda) looks fantastic under a dark sky, and dust lanes are visible. Dimmer DSOs are quite within the reach of this instrument, with M1 (Crab Nebula), M33 and M51 all visible under dark skies. Globular clusters also make good targets, although perhaps a little more aperture would be useful here to see them at their best. Working at high magnification, the ST102 is quite capable of splitting the "easier" double stars such as Castor and Sigma Orionis. A 5mm EP works well here, and a Barlow can help to increase the separation on brighter doubles. The dim companion to Rigel can just about be made out under good seeing conditions. You may notice that I haven't mentioned CA (chromatic aberration) yet. That's because, for clusters, DSOs and most double stars it simply isn't an issue. For planets and lunar observation, however, it's a different matter. Yes, the dreaded purple haze is there, especially noticable on the limb of the moon and on bright planets such as Jupiter. In fact, the ST102 is quite capable for casual lunar and planetary observing, but if the solar system is a primary interest for you then you might look elsewhere. Although the optics are pretty sharp at high magnification, I really feel that the CA damages the contrast for planetary and lunar observation. This is my first refractor (my other scope is a 10" Dob). I have to say I'm now a refractor fan! There's something about the ease of setup and the contrasty, pinpoint stars that appeals to me. I also like the short-tube concept from a portability point of view, and these scopes are very capable deep sky instruments. Yes, CA is a problem on bright objects at high magnification, so it's not an all-rounder like an APO, but for the price it's fantastic value for money. I mentioned the focuser earlier. After some use, the focus tube developed some vertical play. There are two grub screws on the top of the focuser which are used to tension the drawtube. I needed to tighten the front (i.e. closest to the objective) screw to take up the slop, and also tighten the rear screw to remove any remaining image shift. After this adjustment the focuser worked fine again. I have now had to do this twice, so it seems that periodic adjustment is required. After the second adjustment cycle the focuser was very stiff, which I resolved by slackening off the screws that tension the spring in the focus pinion assembly. Now the focuser is nice and light and smooth, but I anticipate further adjustments will be necessary in future. We shall see! This is really a faff and the only real annoyance with this scope. There is a dual-speed Crayford focuser available which is a drop-in-replacement for the original R&P focuser, but at around £129 I'm not sure it's worth it on an OTA costing £169! All in all, I really like this scope, apart from the cheap focuser. In fact, I like it so much I'm wondering what the 6-inch ST150 would be like on DSOs and clusters! Ed
  4. If you want the wide field of view that a 2" eyepiece offers, then they are well worth it.
  5. I'm not a fan of the "mobile" layout when using a tablet. Is there an option to see the desktop layout instead when using a tablet?
  6. Thanks, that's useful feedback. I also have the Porta II mount, so it's good to hear that it works well with the Mak 127.
  7. Yes, you're right. Actually I thought I might splash the extra £100 for the version on the Synscan AZ goto mount. That version has the dovetail on the side instead of the bottom. Then I would have the option of using it on the goto mount for tracking or the Porta II for quick views. And I can also use the ST102 on the goto mount as a bonus!
  8. Shouldn't be a problem. I don't intend to use it for wide fields (I have the ST102 for that).
  9. I'm not expecting it to better the Dob, I just want a small scope for grab and go that performs well on planets/lunar. The Dob is too heavy to haul out just for a quick look at the moon.
  10. Thanks, that makes sense. The Mak should complement the ST102 with its colour-free views. Further in the future I could consider upgrading the frac to an ED if I feel the need.
  11. Thanks for the comments so far. My heart says Tal, but my head says Mak due to its more compact size! Good point about the 100ED, Moonshane. I already have the ST102 for wide field views, but I could consider the 100ED as a future upgrade path.
  12. I currently have a nice 10" Dobsonian complemented with a ST102 f/5 achromat for grab-and-go sessions. Whilst the Dob is a great all-rounder, the ST102 shows its weaknesses during Lunar and Planetary viewing (mainly limited contrast due to CA). So I'm considering getting a third scope dedicated to lunar/planetary. Currently I'm considering the TAL 100RS and the Skymax 127 Mak. Very different beasts, but essentially both long focal length scopes with 4-5" apertures. Which do people think would be the better choice? I'm aware there will be some CA on the TAL, but how troublesome is it? What I'm looking for is crisp, satisfying views of the moon and (as far as seeing allows) planets. Other suggestions also welcome! Ed
  13. Hi Bobby1970, Do you find the Mak 127 to be a good complement to the ST102? I'm thinking of getting one for lunar and planatary observations (possibly on an AZ Goto mount). I agree the ST102 is surprisingly good for planets, especially as a grab-and-go. The CA does annoy me on the moon though! Ed
  14. I decided to get up early this morning (5.30am) to try to get my first look at Saturn as well as the other 3 planets on show at the moment. Given the lack of time this was a good opportunity to give my new Startravel 102 a proper test. My 250PX Dob stayed in the garage - I didn't have time to wait for it to cool down before observing. First I checked out Jupiter with the 5mm BST EP on the ST102, giving 100x magnification. A nice sharp image, some CA visible, but not overwhelming despite the brightness of the target. Meanwhile, Saturn was rising over the nearby hills. I slewed over to it, but it was so low that it only appeared as an orangey oval blob. So, I decided to spend the next while checking out some globular clusters (only easily seen in the early morning at the moment). Using Stellarium on my phone, I easily located M3. It was a bit feint in the 102mm frac, and averted vision helped with this one. M5 on the other hand was much more impressive - I could clearly resolve individual stars. Next on the list was M13, the great cluster in Hercules. Actually I was slightly disappointed with this one - although it was a nice object, I found M5 more impressive on this occasion! I had a look at the double double (Epsilon Lyrae), which was a challenge to my little refractor. I could clearly split the southern star pair, but the northern pair eluded me. Must try again with the Dob! By now (6.25am) Saturn was well up. Now the rings were clearly visible - as everyone knows, seeing this for the first time is a real "wow" moment! It was still fairly low in the sky, so turbulence and dispersion disturbed the view quite a lot, so no Cassini division or other details were to be seen. But at least I have seen it now! All in all, a good performance by the ST102. My Dob is feeling decidedly unloved - I'll make sure I take it out next time! Ed
  15. They work great with 2" wide field eyepieces like the Panaview 32mm, giving a whopping 4.4 degree field of view. Fantastic on the Pleiades and Perseus double cluster. On the other end, I sometimes use a 5mm with a 2.5x Barlow for 250x magnification on double stars. The 5mm on its own is good for planets and the moon.
  16. Just a follow up on this. FIrst, I tested a Revelation 1.25" diagonal in place of the original 2" diagonal, and found that the problem with the star shape went away. Pretty sure now that my diagonal was at fault, I bit the bullet and ordered a new Revelation 2" quartz diagonal. Tonight, despite the bright moon, I had lovely still skies to test the new diagonal with, and bingo! - perfect Airy discs. My view of Castor now appeared as two nice bright spots at 250x magnification instead of two elongated "cats eyes". So somehow I had indeed damaged the original diagonal - either by scratching it or by perhaps minutely deforming the surface somehow so that high magnification views were disturbed. Anyway now I'm happy, and I'm actually pretty impressed with the performance of the little ST102 coupled with a decent diagonal and eyepieces. Ed
  17. Clear sky forecast here tomorrow morning... I'll be setting my alarm! Whether I can drag myself out of bed is another matter!
  18. Those Rolson handles look great! Does anyone know where I can buy them?
  19. I went with the ST102 with a manual alt-az mount as my travel scope rather than the Celestron as I didn't want the added complication of a go-to mount and batteries to worry about. Also the ST102 is slightly shorter (being f/5 rather than f/6). You would probably still need to remove the dew shield to fit it in hand luggage, however. I think the Celestron and the Skywatcher are made in the same factory, so quality should be very similar. Theoretically the 102SLT should show slightly less CA, but I doubt you would notice the difference in practice. Either will be fine for DSOs from a dark site. The Celestron might have the edge for planets. Ed
  20. Yes, I think I prefer Robert the Robot to that creepy Brian Cox! :-)
  21. Anyone else with young kids watching CBeebies Stargazing this week? They had a nice spot this evening from Jodrell Bank on stars being born in the Orion Nebula. My 4 year old daughter was excited to come outside with me afterwards and look at stars being born through my telescope! Sadly Orion was a bit low in the sky for the best view, but she was still thrilled to see anything at all. Great stuff!
  22. Thanks. I have taken the diagonal apart to check, and the mirror is a thick chunk of glass (or quartz presumably?!) pressed flush against the body of the diagonal by a foam pad. There is nothing that can move, and I have checked the collimation of the diagonal itself using a laser and a mirror - the beam reflected back, bang on the centre spot on the laser collimator. I haven't yet checked the beam alignment through the whole scope as you suggest, so I'll have a look at that tonight.
  23. Hi, I recently purchased a Skywatcher ST102 f/5 refractor to use as my grab-n-go scope. I was putting it through its paces last night and I have a couple of queries regarding star diagonals. (I'm quite new to all this!) I currently have an Altair Astro 2" Quartz Dielectric diagonal. Altough it seems to perform well at low magnifications, I noticed something like astigmatism at high mags (above 100x) - basically, stars were appearing slightly elongated unless the focus was absolutely spot on. I then tested the scope with the diagonal removed (using an extension tube instead) and saw that most of the "astigmatism" went away. More strikingly, without the diagonal I was able to clearly split the double star Rigel in Orion at 200x, whereas the view of Rigel through the diagonal was less crisp and had lower contrast, and hence the companion star was nowhere to be seen. Now, I have a confession to make! Last week I managed to drop a Cheshire eyepiece into the diagonal (ouch!), and there is now a small scratch near the middle of the mirror (maybe 1.5mm in size). In fact, there are two such scratches very close together. Is it possible that this small mark is messing up the performance of the diagonal at high magnifications? I am really quite surprised by how much the diagonal degrades the view at high magnifications. I didn't realise a simple mirror could have so much effect! Should I be looking for a more upmarket diagonal, or is it likely that I've damaged my diagonal with my misadventures? I'm willing to replace it, but don't want to waste money if it's likely to make no difference. Thanks, Ed
  24. I have a Skywatcher 10" Dob. I live in East Devon, where there is some light pollution, but I imagine much less than in the London area. However, I feel I'm not getting the full benefit of my 10" aperture simply because the light pollution is limiting my ability to see faint objects. Also, bear in mind that a 12" Dob is a large, heavy instrument to have to carry in and out of the garden. If your main interest is solar system objects I wonder whether you might be better served by a smaller Maksutov-Cassegrain or Schmidt-Cassegrain telescope? You won't need the light gathering power of a 12" for planets, although the larger aperture does give higher resolution (atmospheric conditions permitting). You are right that with a Mak or SCT you will lose the ability to get really wide-field views, but if this isn't your primary interest then maybe you could supplement it with a wide-field scope at a later date? Just a couple of thoughts!
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