Should I get a 3” frac?

[IB20]

I have an 8” dob, which I love, but having recently had a baby I’m finding I struggle to have the hobby time to plonk it outside for cooling and then have adequate viewing time! Also the weather over the last few months has been somewhat changeable but there have been noticeable periods of cloud break, which got me wondering if a ‘grab n go’ frac would be a good tool in my armoury?

Ideally something I could get outside and be viewing within the drop of a hat. I’m fully aware that my dob will provide better views on every target than any 3” in existence but have a few questions with the below statements in mind:

Targets - mainly solar system objects planets, lunar, asteroids, white light solar, bright sky objects - M31, recent nova in Cas etc

Bortle 7-6 skies, the later it gets

Budget - £1000ish

1. Would a 3” frac make a suitable complementary grab n go scope to my dob?

2. Would a 3” frac be better than 20-25x bins?

3. Would a 3” frac be affected less in poor seeing than my dob, I’ve had a few session when the jet stream has been over the UK which has just been bleurgh.

4. Doublet, triplet? APO or Achro?

5. Recommendations, I know nothing about mounts, tripods, diagonals I.e frac things! (I am eyeing up the Vixen SD81s).

By all means, feel free to go off piste if you’d recommend a different direction of travel.

Thanks kindly!

 

 

[GazOC]

With that budget I'd go for a 4 inch for doublet for visual, it's fairly big step up from a 3 inch but is still pretty easy to set up and mount 

[Stephenstargazer]

In terms of carry out, put down and point at an object, there is not much time difference between the dob and a moderate refractor at the same magnification. For very brief grab and view nothing beats binocualars, so why not start with some 8 X 40 and see how it goes before spending more?

Having said that a 3 "  on a small mount would be a good companion to the 8" Newtonian.

Edited April 11, 2021 by Stephenstargazer

[IB20]

3 minutes ago, Stephenstargazer said:

In terms of carry out, put down and point at an object, there is not much time difference between the dob and a moderate refractor at the same magnification. For very brief grab and view nothing beats binocualars, so why not start with some 8 X 40 and see how it goes before spending more?

👍🏻 I have 8x42s and 15x70s, I’ve been offered some 25x100s. If the consensus comes back binos then I’m happy with that. 

[GazOC]

Mounting a pair of 25x100 bins is a bit of a drama, not really grab and go 

Edited April 11, 2021 by GazOC

[Peter Drew]

No comparison really, two different instruments with different strengths.  I think a 3" or thereabouts refractor would complement your current binoculars and Dobsonian better than an extra binocular.

[Mike JW]

Don't forget double stars - much pleasure to be had from observing them. If possible I would go for a 4" refractor.

[michael.h.f.wilkinson]

I did a comparison between my 80mm triplet and a pair of Helios Apollo 15x70s I used to have (since replaced by the Helios LightQuest 16x80). It might be useful:

 

[IB20]

10 minutes ago, Mike JW said:

Don't forget double stars - much pleasure to be had from observing them. If possible I would go for a 4" refractor.

Oh double stars will be the one of the primary targets, not sure how ive missed them off 😂

[IB20]

9 minutes ago, michael.h.f.wilkinson said:

I did a comparison between my 80mm triplet and a pair of Helios Apollo 15x70s I used to have (since replaced by the Helios LightQuest 16x80). It might be useful:

 

Thanks for this, your report is extremely helpful!

[cloudsweeper]

With that budget I'd go for a quality 4" short focus frac on a nice alt-az mount.  Nice wide views, ease of use, and enough aperture to spot faint stars in doubles etc..  And for closer doubles, you can use a Barlow.  

Also - you'll be impressed with the sharpness of stars in a nice frac - much better than a Newt/Dob or a Catadioptric.

Doug.

Edited April 11, 2021 by cloudsweeper

[KP82]

A 90-102mm short tube apo would be my choice. They are as easy to set up as the 3" but the amount of extra light they can gather is very noticeable unless you want airline portability.

And for visual only a quality doublet would do.

[Luke]

I'd go for a 100mm refractor if it was me. Lots of good options here. I have the Skywatcher ED100 DS Pro (F9). It's a bit long but very light for its size and is a joy to use on a giro mount. It's very good for white light solar and nice on the moon. It's not a bad time to be getting a solar option, nice and early in the new cycle.

Solar is lovely as you can just do five or ten minutes and be happy. I have four refractors from 60mm to 120mm and I would probably keep the 100 over the others. It's just a nice balance of aperture to weight and for my taste shows plenty of lunar and solar detail.

My wild alternative suggestion is get a solar h-alpha scope, possibly second hand. Something like a PST, Lunt 50, SolarMax 60. Although it can only observe one object, it's different every day and sometimes changes a lot in a matter of minutes or hours. It might be compatible if nights are a problem and may see a lot of use.

Good luck picking the right option for you.

Edited April 11, 2021 by Luke

[Alien 13]

Think about focal lengths, no point in having two instruments with similar, If it was me I would go for a 70mm ish APO..

Alan

[Neil27]

My take -

4 inch refractor, at say f7, this one

https://www.altairastro.com/starwave-ascent-102ed-f7-refractor-telescope-geared-focuser-468-p.asp

Mount this one, with steel leg tripod

https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/skywatcher-skytee-2-alt-azimuth-mount.html

Finish with extender for comfortable viewing, 

https://www.firstlightoptics.com/sky-watcher-mount-accessories/skywatcher-eq5heq5-extension-tube.html
 

Total £1029

This would be my choice, keep eyes peeled for second hand items and probably get the lot for £700 to £750 ish pounds. Leave some extra pennies to buy a nice diagonal and eyepieces .. 👍

Good luck, always fun spending other people’s money 😉

Edited April 11, 2021 by Neil27

[Stu]

I would second the idea of a 4” f7 ish apo doublet. The focal length would be sufficiently different to the 8” to give you widefield options unavailable with the dob, yet it will still give excellent planetary, lunar and solar views (with a wedge), as well as doubles of course.

If your budget doesn’t include the mount then something like the Technosky 100mm f7 with FPS-53 glass might suit at £989, or perhaps the Starwave Ascent 102mm f7 which seems to be a great value scope at £495, cheaper glass but I have seen good reports on it.

[Commanderfish]

For those quick opportunistic views you want a light scope which you can carry out preferably already mounted.

Definitely go for an Alt Az.mount, not an EQ. A Giro like those from Teleoptiks works great. Keep an.eye.out for.a.uaed wooden.trupod like a Berlebach. Light, sturdy, absorbs vibration - but a cheaper aluminium one will do if the scope is light and short enough.

You want a scope that will cool fast, so a doublet. At your budget (especially buying used) you can probably get one with high end glass like FPL51 or even FPL-53, so.youre basically looking at an Apo doublet. I would go for 90-102 mm aperture  and 600-700mm FL.

Longer scopes are harder to mount stably and have narrower fields.

As to targets, there are lots of things which a frac like this will actually do a lot better than either your dob or binos. These scopes are sharper than newts and show lovely wide starfields with high contrast. Yes a newt will  beat them on galaxies, but youre not going to get a three or four degree starfield out of a newt and you cannot get anything but the very lowest magnification out of binos.

The whole of the Orion's belt region in one view, the whole of the sword, the whole of the Pleiades, there are many things these do really well on.

Edited April 12, 2021 by Commanderfish

[Dazzyt66]

For me, my ultimate grab and go is my ST80. It’s light (mine travels all over with me - when we can do that again!), no cool down required, fits on pretty much any tripod (I’ve got a lightweight aluminium camera tripod I travel with), they even come with a small desktop eq1 which can be motorised and it’s field of view makes it easy to move around the sky (although I do use a red dot with it too). If you are only doing visual this works well on moon, planets and DSO - and you can spend your remaining £850 on accessories 😀 

Of course, with your budget you could also go for a bigger ST (102 or 120) or the ED80 and still have plenty of change from your £1000 although you’d probably need a more substantial tripod with those.

HTH

[Mike JW]

As to which mount, I have always used a GOTO mount - you get to see so much more especially if time limited. I have had an iOptron MiniTower Pro for years and observed hundreds of doubles, much lunar sketching using this mount, as well as bright DSOs.

Mike

[ollypenrice]

If you don't have a very dark site I'd go for 4 inch over 3 inch. There's not much difference in bulk but a big difference in what you can see. (I live at a very dark site and do find a 70mm good visually. Rosette, Veil, etc.)

Alt-Az for sure. I use a very old and very second hand TelePod but it's fine. Also good for wildlife, if bulkier than a true spotter scope.

Mike JW makes a good point about the Mini Tower, though.

Olly

[michael.h.f.wilkinson]

+1 for the mini-giro. It easily handles my dual solar set-up, either on a very light carbon-fibre tripod or on a home-made wooden tripod (with a tiny piece of EQ-2 tripod holding bits together). It can handle a lot more weight than just the 80mm. I am not a great user of go-to, especially for quick sessions. On outreach events I find I am up and running while others with go-to rigs are still trying to get star alignment working. By the time they can observe, I have spotted a couple of DSOs already (up to half a dozen). No go-to means no battery, means one less thing to go wrong or forget. Don't forget these wide-field refractors allow easy star-hopping, so a finder scope is hardly necessary.

Regarding 4" vs 3": my 80mm is airline portable, I am not sure a 4" would be, but I am not sure it is a requirement.

 

[badhex]

This might be an unpopular opinion but... If you're willing to spend a pretty small amount of money as a 'test' budget, you could see if you can pick up a pre-loved Celestron Travelscope 70 (just the OTA, none of the rubbish accessories). It's by no means an "incredible" scope but once you get it together with a half-decent EP/diagonal/mount it punches well above its weight for the price - and the whole kit is currently £85 on the large well known retailer, so you should be able to find a used OTA for significantly less. This way you can test out if the aperture vs. convenience factor works out for you without spending tons - although you'd need a mount and diagonal regardless.

The reason I'm suggesting this is that I picked one up on impulse while on holiday with reasonably dark skies. I'd expected it would be basically a bit rubbish and relegated to holiday usage only. Once I got it home and paired with decent kit I've had so much fun with it that I am replacing the scope with a TS-Optics 70ED doublet eventually, which is nearly like-for-like in physical size, FL and aperture, but obviously a much better scope. Below shown with a Skywatcher AZ-GTi go-to, Skywatcher di-electric 1.25in diagonal and Baader Morpheus 17.5mm (which gives genuinely spectacular views - the whole pleiades in one view blew me away).

Anyway - this was my experience - hopefully it is helpful!

 

 

[IB20]

Really appreciative of all the comments, lots of experienced members suggesting 4” frac which I think I’ll start looking into. My idea was to buy a Tak 100XX for my retirement in 20 years, I guess I could start saving for that now, but feel I’d like to learn how to use and care for a frac before jumping in at the very highest end.

The Altair 102ED F7 looks like a really good bit of kit for the money and not much heavier than than the SD81s or Stellamira 80mm. 

I’m not really much of a goto fan, I don’t really struggle to navigate and take enjoyment from locating some hard to find targets. Airplane travel is not really required at this stage, but portability to a UK dark site now restrictions are lifting would be welcome. 8” dobs and baby car seats are not compatible!

 

 

 

[Paz]

I have a 72mm f6 and a 102mm f7 and I only use the smaller scope if I'm taking it somewhere where it has to be a really small/light scope.

At home the 102mm gets all the action because it is just as fast to set up and cool down isn't an issue.

So I would recommend a 4".

Edited April 12, 2021 by Paz

[ScouseSpaceCadet]

Since downsizing to a 4" f7 ED refractor I haven't been disappointed. DSO observing with my previous 8", 6", 5.1" reflectors and 120mm f5 achro refractor was slightly underwhelming due to the light polluted skies so I'm not missing anything in that respect.

What I have gained is a pin sharp lunar, planetary, double star and wide field views. Magnification can be pushed past its limits somewhat, punching through the lp. CA and diffraction spikes are not issues. The scope is easily mounted and quick to set up.

 

 

Edited April 12, 2021 by ScouseSpaceCadet
'ED'