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Cosmic Geoff

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About Cosmic Geoff

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    Sub Dwarf

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    Bucks, United Kingdom
  1. Cosmic Geoff

    Family scope

    I'm not a fan of Dobs but since the mount is very basic they offer the most aperture for your money. For £200+ you might get a 6" Dob or maybe an 8". Any difficulty in moving it around will be because of its bulk rather than the Dob design. In theory you could re-mount the tube on a different mount later but in practice you may find it less bother to dispose of the whole outfit and buy again, particularly if you are not into DIY. If you buy a small scope you could keep it as a handy second scope, holiday scope or grab'n go scope, should you buy a bigger instrument later (as you most likely will if the astronomy bug bites). Think of your first scope as an exercise in finding out what you like or don't like about amateur astronomy and/or telescopes. In my case: Like: GoTo, quick and easy setup, power tracking, choice of scopes with different mounts, RACI finder. Don't like: Big scopes with no GoTo, long heavy scopes, time-consuming setup, wobbly tripods, straight-thru finder.
  2. I would just like to point put that most of the weight in a SCT OTA is in the mirror at the back end, accordingly the centre of gravity of the tube will not be halfway up, but near the back end. Adding heavy accessories such as big eyepieces, cameras etc will shift the centre of gravity even more toward the back end. So with the Celestrons, you should clamp the OTA as far up/forward as it will go in the dovetail clamp and then forget about 'balancing' it. The clutch and gear train will hold it. (remember the brass rod that props the OTA up in the old fashioned alt-azimuth mounts .) Also worth noting that a severe imbalance caused e.g. by moving the OTA back/down in the clamp will move the centre of gravity away from the mount axes and may be expected to make any vibration worse. I found my C8 SE quite badly behaved as regards backlash, particularly with the weight of a camera on the back end. Possibly because the balance was too good, but it is actually impossible to tell with it assembled. I may be wrong, but the Evolution mount for the C8 OTA seems to be sized for the C9.25, so a slight advantage there over the SE mount used on the C6 and C8 SE. But the C8 SE and C8 EVO have the same tripod. I would also say that while these mounts are not as stable as one would like, this is a compromise. You could (I could) buy a heavier and more stable mount, but it would be heavier, cost more, and most likely be less convenient to use. For instance, if I had an AZ-EQ6 mount I don't see myself carrying the whole mount/OTA outfit out of doors in one carry!
  3. Does the first image show Comet 46P/Wirtanen just below two stars at mid height on left?
  4. You can move the OTA about the altitude axis by applying enough force to slip the clutch, otherwise, no.
  5. Speaking as a mechanical engineer, I would say that there is no need to worry about balancing the 9.25 Evo around the altitude axis. The clutch and gearing will resist any imbalance. Experience from the USA reported on Cloudynights indicates that the C8 SE can be operated for long periods with significant added unbalanced loads without ill effect. And the SE mounts reportedly have plastic gears while the EVos reportedly have metal gears which should be more durable. As JG777 says, operating with a front load may well confer a practical advantage. For one thing, perfect balance may just increase annoying backlash. It is actually quite difficult in the absence of a manual clutch to tell whether these power alt-az mounts are balanced or not.
  6. Cosmic Geoff

    Comet P46/Wirtanen

    After a couple of failed attempts on earlier nights, I observed the comet on 12 Dec around 9pm with my GoTo C8SE (203mm). Easy to see. This is an urban location and the sky was accordingly poor so I assume what I saw was the bright central core. I looked for a couple of ~9th mag comets currently in the sky but could not see them.
  7. Why? Can you upload a photo showing why it won't go above 70 degrees? My C8 has about 2cm clearance when pointed vertically with the 1.25" diagonal, so there is a sporting chance it would clear a bulkier 2" diagonal. My reference to imaging was because mounts like the NEQ6 used for imaging are clearly very stable. It follows that mounts intended for visual only are likely to be lighter, more portable and less stable...
  8. By all means try it, but in practice you will find that it's not that easy, otherwise everybody would be doing it.
  9. The GoTo mount commonly bundled with the 130P can be bought separately. This would be cheaper than the Discovery mount but has fewer features and is less robust. To use Stellarium you would need to connect a laptop by cable. As mentioned above, you could mount your OTA but watch out for where finders and focuser end up if the previous mount is an equatorial.
  10. I saw one of these C9.25 in a showroom a month or two ago, lined up with other Celestron scopes including the C8 and the EVO 8. I could see that the C9.25 has a chunkier mount and tripod than the C8 (=mine) but the scope is chunkier too. The EVO 8 tripod looked like mine. This sounds like the same complaint often levelled against the SE6/8 mount of the very popular C8- that it's not steady enough for the weight of the OTA. To which I respond: true, but it's a portable visual mount, not an imaging mount, and if you want a mount with a higher level of stiffness, buy accordingly.
  11. In answer to your questions, my manual quotes 750ma for what is actually the same mount as used on the C6. So 1.5 amp ought to be enough. However it does no harm to over-specify a bit so you can use the same PSU on any GoTo you acquire. Some people may try to persuade you that you need a special outdoors supply that will work in low temperatures. A good quality supply ought in theory to have a spec that includes the temperature range. The limiting factor is the electrolytic capacitors which have a limited working temperature range and lose capacity at low temperatures. However I looked up some capacitor specs and it looked as though the observer would freeze up before the PSU did. So don't worry about this if you live in a temperate climate like the UK. Also bear in mind that electronic devices are self-heating to some extent. As others have said, 240v is lethal so don't allow the outside equipment to get wet and then touch it. AFAIK Celestron and Skywatcher never supply a mains PSU with their outfits. Celestron may supply a car connector lead.
  12. It doesn't particularly matter which mains-DC power adapter you use, so long as it is regulated, can deliver up to 2 amps or so, delivers the power with the right polarity and via the right 5.5/2.1 mm plug. (The manual for my C8 says it needs 750ma.) If you scan the forum, you will see that members have used 57 different varieties of battery or power pack to power their GoTos. Note that you may need extra power if you add dew heaters and suchlike. That's entirely true. I had to ease open the centre prong on mine with craft knife, and I use a stick-on aluminium tie to restrain the cable. One would think that the aluminium prongs would fatigue and fracture from the repeated opening and closing around the cable but it's still good after nearly two years! I use another stick-on tie as a hook to park the handset in a more convenient position while observing.
  13. What are you going to mount the 10" Newt on? If you intend to do planetary astrophotography with it, you will need a SERIOUS mount for it. If your prime aim is astrophotography, an 11" SCT on an equatorial or fork mount might prove smaller, lighter and easier to manage, and possibly even cheaper given that the load will be less. If you look in the Planetary Imaging section of this forum, you will see that many planetary imagers use SCTs, which work well in this role. The depth of focus of a SCT makes it easy to attach cameras and other accessories such as ADC, flip mirror, filter wheel.
  14. A fine result. The colours look about right. I assume this is with the 80ED. Which camera?
  15. I imaged the conjunction around 17.30hrs GMT with my Startravel and ASI120MC camera on the SLT mount (+fixed wood tripod). The image scale with my C8 would clearly have been too large. The image, processed in Registax6 from 200 frames, is shown below. The image is shown horizontally flipped to match the telescopic view with star diagonal. I puzzled for some time over what exactly I had captured, but the centre dot is Mars (overexposed) the faint dot at lower L is Neptune, and the brighter dot at upper R is the star 81 Aqr. I also took a run which has Mars only slightly overexposed, and looking very small, and inevitably not capturing Neptune.

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