Capstone55

I'd second the advice to get two scopes if you can afford to. Visual and astrophotography are almost like two different hobbies as far as equipment is concerned. Visual astronomy is much less expensive to pursue compared with astrophotography and a 8 - 10 inch Dobsonian should suit you well and you'll start to learn the sky while using one. As others have said, the mount is critical for astrophotography. Together with a decent refractor, you're looking at the thick end of £2000 to get set up (and that's without cameras).

It really is difficult to account for atmospheric chemistry producing PH3 at those levels, especially as it'll be oxidised pretty quickly (in an extremely oxidising environment with 85% H2SO4 floating around). But you can't exclude something unusual and non-biological. It'll prompt a lot of searching for answers and questioning of the original PH3 data (though it has been confirmed with two independent radiotelescopes, so seems robust) Nevertheless, if life is eventually proven, it'll mean a Nobel Prize for Jane Greaves and a couple of the others, and it'll mean that life is widespread throughout the universe, so very exciting.

Generally, for visual astronomy, the bigger the aperture the better. Particularly for DSOs. But you'll be mainly looking at planets, which are bright, so aperture becomes a little less critical. Refractors are usually good for planets but you'll be limited with the number of DSOs you can see, though as you say, a 90mm will be good for the brighter ones. You might also consider a catadioptric scope like a Schmidt-Cassegrain or Maksutov-Cassegrain which with their long focal lengths, produce a big image of planets but are not optimal for DSOs. Personally I find planets rather underwhelming in an amateur scope, and don't often look at them. I think we've been spoiled by all the space probes that have visited the outer planets and sent back stunning pictures. Sadly, with a small scope under a blanket of air, the view is disappointing (in my opinion, which many may not share). So, I much prefer DSOs but I have a 10" Dobsonian which shows them well.

I have a long Cheshire (Astro Essentials) and to be honest, I mostly use a simple collimation cap. The Cheshire is too long for me to see the whole of the primary when aligning the secondary (admittedly not done very often). The Cheshire is better for aligning the primary but the collimation cap is good enough so I usually use that.

Thanks for that....very useful and will have a look at Nirvanas. I've seen elsewhere that Hyperions don't do well in a fast scope. Not especially fussy about edge correction but the proof's in the pudding and would consider a coma corrector if I found it an issue. Thanks for not mentioning the unmentionable! 😃

I have a similar question about my f/4.7 Dobsonian. What do people think about the Baader Hyperions or the ES 68 series and the Vixen SLVs? I suppose somebody will recommend Televue's but spending £2/300 on an eyepiece seems ridiculous. Diminishing returns and all that.

Are there any makes of 25mm wide-angle EPs that anybody would recommend for a f/4.7 telescope? I understand that the low f-number creates an optical challenge so I guess that means a more expensive EP. I'm not really restricted by budget but neither am I an EP obsessive and can tolerate some degree of fall-off in quality around the edges of the field. Probably goes without saying that this is for visual astronomy only. Thanks

Thanks very much

Thanks for these interesting responses. Not what I'd considered. One question though. I'm 64 and have doubts whether my eyes can handle the exit pupil of anything longer than a 25mm EP (ie about 5mm). Presumably an exit pupil larger than my pupil diameter will look dimmer? If so, is it especially noticeable and would the wider field of view still be advantageous?

I've just got back to observing by buying a Skywatcher 250p f/4.7 Dobsonian for visual astronomy only. It comes with the usual SW 25mm and 10mm EPs and I also have a Telrad finder, Cheshire EP and neutral density filter for the moon. I have Stellarium and all the books and charts I will ever need. I'm very pleased with it so far but am now considering upgrades. What should I get next? Replace the EPs with higher quality, or initially get a higher power EP or should I get a Barlow? And which filters would be best? Any advice gratefully received.

For general astronomical theory, An Introduction To Astronomy and Cosmology by Ian Morrison, is really good. The maths used is pretty straightforward and not advanced, and it's very readable.

Yes, with non-motorised alt-azt mounts, objects will drift out of the field unless you move the mount manually. With alt-ax GOTOs, they will track the object for you. Incidentally, they'll drift out with a non-driven EQ mount, but only in one axis.

Ah yes, I'd not come across the Telrad before. Can imagine it would help greatly with finding DSOs. Skies are dark where I live but hope to move soon to a smallish town with some light pollution. But without actually trying it, I'm not sure how bad it will be.

Suspect that if you were viewing your chickens through your window, then the problem may be the glass in the window, rather than your telescope.

Thanks, a useful reply and food for thought. I suspect I'm making too many compromises at the start and will seriously consider a Dobsonian with maybe a 250 or 300mm mirror for visual (I know the 200PDS is designed for photography but its FL is 1000mm which gives a smaller FOV than I'd prefer for photographing DSOs...not as interested in moon and planets). If I decide to get into astrophotography, I'll go for the HEQ5 plus scope. I don't want to try the EQ6 as I'd want to (a) run a scope with shorter FL to achieve a good FOV (though the 150PDS may be OK) and will therefore likely to be lighter, and (b) I will want to transport it to areas with darker sky than at home and I've heard the EQ6 is quite heavy. The only mild concern I have with a Dobsonian is actually finding DSOs without RA/Dec scales to get you pointing in more or less the right patch of sky. I know the sky fairly well (and knowledge is coming back) but I years ago, I remember fiddling around for ages with a refractor on an alt/az mount, hunting for galaxies and nebulae which I knew the position of on star charts and was able to find the nearby reference points in the sky. But maybe it was the scope. Or me.

I'm currently researching telescopes after 40y away from the hobby. My interest is predominantly visual astronomy but I'd like the option of doing astrophotography at a later date. So this post is more about mounts than anything else. The telescopes I'm most interested in are the Skywatcher Explorer 150PDS or 200PDS. I know neither of these are ideal for astrophotography and I would plan to get a 80 or 100mm refractor with a shorter focal length, should I eventually take it up. So my question is this: with the 150/200PDS, should I get an EQ5 mount for visual, which I can upgrade to GOTO etc with an add on kit if I do astrophotography? Or should I bite the bullet and get a HEQ5 from the beginning? And any views on whether the 150 or 200PDS would preferable would also be welcome. I'm technically minded so tinkering around with collimation etc doesn't worry me. Thanks in anticipation