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Complementary Refractor


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Hi folks,

I'm looking for some advice on which refractor I should get. A little bit of background first. I bought an 8 inch Skywatcher Dob towards the end of 2015. I used it a few times, but unfortunately I had to move it upstairs into a spare bedroom when we had to reconfigure the house a bit. It ended up stuck in a corner behind a pile of junk and was consequently too much of a PITA to get it out and take outside, so it just sat there unused.

Fast forward to a couple of months ago when we had a garden room extension and I spotted the opportunity to move the Dob down into the dining room. In the meantime I had bought a nice pair of 10 x 50 binoculars and a tripod to nip out and have a quick look at the sky on the rare event that it was clear. I've recently taken the opportunity to look at Jupiter with the bins, as it was conveniently situated in the southern sky for my back garden. Despite being low-ish in the sky and having to look over neighbouring roofs even the bins were able to view it and the 4 moons that looked like white specks. A few days later I managed to collimate the dob and get it outside for a peek. I couldn't make out much colour due to the poor seeing and probably thermals from the rooftops, but Jupiter and the moons looked way better than the bins (obv). I showed my wife and even she was impressed. Mind, I'm not sure what she'll say when I mention getting another scope after hardly using the dob the last 6 years!😅

To be honest it got me buzzing about getting the dob out again as soon as we get some clear skies, but it's been awful for about the  last 10 days. It's also got me thinking about getting out to better skies nearby, which isn't so convenient with the dob. Also there is quite a bit of sky blocked off to my dob by surrounding houses. The skies above my house are Bortle 6, which I know is a lot better than those above major cities, but I can get to Bortle 4 within a 20 minute drive. I've decided that an ideal complementary scope would be something like a 4 inch refractor. The reason being that I could quickly nip outside and use it in breaks in the cloud in my garden, and even use it while waiting for the dob to cool down. I could also just get in the car at short notice and drive somewhere a bit darker and with wider views without having to lug the dob around and have to collimate it every time. Then there's the wait for it to cool down.

So I've been looking on FLO amongst others, and reading loads of reviews, but seem to go round in circles. I'm not sure what the budget is, but it's possible the wife might kill me if I look to spend over £500. 🤪

Obviously I'd like the holy grail of a Refractor that's good for planets and DSOs, but I realise that there are trade-offs for either. Do I get a short tube achro that's more grab-and-go and takes up less room in the house and is good for wide field and DSOs, or do I go for a long tube (say f/10) that's better for planets and has less chromatic abberation, but might be not so good for DSOs due to the narrow field? Or do I go for something in the middle like an f/7 or 8? Apochromatic refractors look like they're going to be way over budget, but I can see the advantages. Then of course there is the consideration of a mount and tripod that will take whatever I choose. I was surprised to see how much some of those cost when you consider how cheap dobs are! I'm only looking to get a refractor for observing.

Anyhow, these are the ones I've been looking at. I welcome any views and alternative suggestions (not a smaller dob). 😁

Skywatcher Startravel 80 or 102 on AZ3 mount for £189 and £249 respectively

Skywatcher Starquest 102 on Eq mount for £269 (not sure what difference is to Startravel 102 apart from colour)

Skywatcher Evostar 102/1000 on Eq3-2 mount for £399

Bresser Messier AR 102/1000 (OTA only) for £239 (but can't find any Bresser scopes in stock anywhere!) I must say I like the look of this one.

Altair Astro 102ED Starwave F7 for £495 (OTA only with no finderscope or diagonal. This is really appealing to me, and I have seen good reports on here, but by the time you add the diagonal, finderscope and mount it is way over budget.

I also saw the Skywatcher Evostar 90/900 with AZ3 mount for only £209, but I don't know if that's any good to be honest.

Are any of the Celestron ones any good?

TIA for any help in deciding.

 

Edited by Bioboybill
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However you put it - you'll need to spend about £500 or even more to get "all-round scope".

One option would be to get two scopes:

ST102 and Mak102

Former will be very good for DSO and wide field but very poor for lunar or planetary, while later will be excellent on lunar, planetary and double stars. Both are short scopes so easily packed / transported and will sit nicely on small AltAz mount like Az5.

You can opt to go for 102/1000 type scope - but that is compromise. You'll be limited in how wide you can go and you'll still have obvious residual CA on high power planetary views.

Better option is to go for F/7 ED doublet 102mm scope - but that by itself is already at £500 or more.

Btw, I would avoid AZ3 mount if at all possible. It is not as good for astronomy.

Even some other alternatives are likely to get you close to that budget. Maybe something like this:

https://www.firstlightoptics.com/ts-telescopes/ts-photon-6-f5-advanced-newtonian-telescope-with-metal-tube.html

+

https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/skywatcher-az4-alt-az-mount.html

That is 6" color free aperture that is still relatively portable - on AltAz mount. Will do wide field / DSO as well as planetary rather good.

If 6" is too much - you can put 5" on it as well (in form of SW 130PDS) or go for this version:

https://www.firstlightoptics.com/reflectors/sky-watcher-explorer-130ps-az5-deluxe.html

Just keep in mind that above scope has only 1.25" single speed focuser.

On a really tight budget and if you really want refractor - take a look at this one:

https://www.firstlightoptics.com/evostar/sky-watcher-evostar-90-660-az-pronto.html

With 70-80mm aperture mask, it will be decent planetary scope - not as good as 4" but decent.

 

 

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Bear in mind a refractor still has to cool down to reach optimum performance. A refractor, mount and tripod takes up more floor space than an 8" dob stored upright. They also take longer to put together once outside.

If you have decent skies just twenty minutes drive, the reflector and dobson base will go into the car easily and the most you should need to do is collimate the secondary.

To raise the height of the dob, there are plastic round water butt stands that fit perfectly.

None of those achromatic telescopes will satisfy you after observing with an 8" reflector, so along with the above, think harder whether the money is worth spending.

 

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Thanks for the replies and suggestions, but I'm pretty sure I'm sold on the idea of a refractor rather than a smaller Newtonian or a mak. I'm surprised to hear the AZ3s are so poor when do many of the cheaper detractors are bundled with them. I suppose it keeps costs down, but at the cost of poorer performance? I really like the Altair Astro F/7 ED. Maybe I should save for that?

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Out of all the refractors you have mentioned, the 102ED f/7 is by far the best. It would need mounting on an AZ4 minimum, though these have no slow motion control. If you wanted an EQ mount then an EQ5 is the one to get. If you looked on the used market you could probably pick up a 4"ED for about £400, maybe a little less. A used EQ5 could be found for £150-£200. So even buying used, it will stretch your budget and like you mention, you will still need to get some accessories as well. At the end of the day telescopes are precision optical instruments and they are NOT cheap. It's just a shame that there are so many budget scopes out there that try to look like real telescopes but unfortunately are not. Old advice from Sir Patrick Moore was, buy a pair of decent 7x50 binoculars and learn the sky whilst saving up for a decent telescope. And it's true, there is nothing worse for a beginner to have their enthusiasm dampened by the inferior performance of a toy telescope on a toy mount.

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I haven't experienced all the scopes on your list, but what I can say is:

  • An ED scope should be better for planetary observing than an achro of similar spec, with better contrast and better results at higher magnifications in general
  • F7 is a good focal ratio for a 4" refractor - not too small to test the lens and not large long to be unwieldy - my F10 4" achro now seems very long and cumbersome to use by comparison
  • A pair of binoviewers will work really well for planetary and make it seem like a much bigger scope (although not everyone gets on with binoviewers) 

I've been super happy with my 102ED F7 and it complements my 8" scope really well, the latter being better for faint fuzzies.

Personally, I'd save up for the 102ED and budget for some binoviewers for next year when Mars is high in the sky! 

Edited by RobertI
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