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Moving from 4" achro to 6" achro

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#26 DeanD

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Posted 15 August 2022 - 07:10 AM

BTW, here is the 150 f5 from a different view on the M2 mount:

 

2018-02-02 16.52.27.jpg

 

 


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#27 Astroyesmer

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Posted 15 August 2022 - 09:27 AM

Thanks for the post DeanD!

I was actually trying to find this very telescope but yes it has been discontinued. I suppose low focal ratio 6 inch refractors aren't that popular amongst all the wider dobs on the market for dso observation.

I figured I do need a longer tube anyway since I love watching planets as well. A f/8 6 inch is what I am eyeballing right now and that would be the Celestron VX6.

Too bad it doesn't come with an Alt AZ mount because I have no interest in photography, but I realised I am always frustrated to have to fine adjust my 4 inch Omni AZ102 at 5mm on Saturn: with the goto electronic EQ I suppose it will feel like luxury to just have to keep my eye in the piece and forget the knobs...
I suppose the arrow keys on the remote will allow me to fine adjust manully anyway when I need to! (If anyone reads this and want to confirm)...

I am not ready to buy the scope right now because budget (I also want to add a few accessories in the order - a binoviewer, some 2" EPs, 2.5 or 3xBarlow, powertank etc...) so I will keep using my lonely 4" for now but I love it: it follows me in every trip across the Midwest and is incredibly light and fast to setup. It does shake a little for 3 seconds everytime I touch it but it is not that bad. And at 660mm and 102 aperture it has CA only until I mask the dewshield with the cap center removed. It then turns into a 660mm 2 incher and no more CA.

That is to say I know the Omni series and can vouch for the optics quality at their price range (I got mine for $150 on sale) as well as for the built quality. I was eyeballing the 5 inch Omni 120 XLT but I now feel confident I will eventually get the VX6.

The size and weight are fine for me, and it will be transportable to my go to 4 bortle sky campground park 15min from my home. I will also bring it to darker skyes further away from time to time but I will still use the 4 incher for some family trips where skywatching won't be a priority but a bonus.

I now have to make peace with patience until I can make the order!


Edited by Astroyesmer, 15 August 2022 - 09:35 AM.

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#28 gitane71

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Posted 15 August 2022 - 10:22 AM

   viewing, not exactly the comparisons you wanted, but years ago, I saw a comparison between two 6" refractors and an 8" Newtonian. 

We looked at the trio in Leo.  The galaxies were definitely 'brighter' in the 8" Newtonian but the 'faint' galaxy was easier to see than in 

the refractors than in the Newt.  One refractor was 'oiled', not airspaced while the other refractor was airspaced, but neither of them 

were 'coated' in any way.  The oiled lens showed the galaxies 'brighter' than the airspaced lens, noticeably, but not hugely different.

I do have 60mm - 90mm, 4" and 5" refractors,(all achromats) but haven't had them out at the same time with the 6" refractor for 'comparisons'. 

I would say I use the 6" f/10 refractor at least 90% of the time though just because it is so versatile.  Though I have very much enjoyed

views through some of the smaller refractors, the extra light from a 6" is a significant benefit.  I 'understand' aperture fever, but I also 

think a 6" refractor can be less expensive and easier to live with than many 'light buckets', very efficient and cost effective.  

  Especially if you are not interested in astrophotography, I would recommend getting a used 6" refractor and making your own mount.

That might seem daunting, but years ago, it seems most amateurs started out by making much of their own equipment.  I would agree 

you'd want a tall mount, but that can certainly be done, too.  It could be much cheaper, get you going sooner and you could make it the 

way you want it.  Build the mount out of 'junk' you can leave outside and you'd only have to carry the scope out.  I wouldn't worry much

about the coatings, but also assume that most recent 6" scopes would have at least basic coatings that would help with light transmission

and would help with deep sky views.   

   I've heard early 6" f/8 achromats varied in quality.  If you buy it cheap enough to begin with, it could be a way to learn things about the 

scope and become a dedicated low power or 'binoscope', give you time to hunt down another, better quality, maybe longer scope.    


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#29 Astroyesmer

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Posted 15 August 2022 - 12:09 PM

I totally understand the wise advise but I am kind of a sucker for esthetics when it comes to my "gear"... I also became increasely attracted by a goto mount recently, since the catalog and efficiency of those toys are quite spectacular, even if I probably will use it "manually" most of the time!

But from my research about the VX6 I already know I will make a DIY extension pier to put inbetween the tripod and the mount, so there will be some scrap assembling in the story. I don't want to be concerned about the diagonal hitting a pod or about crawling on the ground for zenith observation...

I have been using the small 4" a lot and feel now ripe for something a little more on the fancy side so to speak. I am still a total newbie about the sky I confess, but feel like I know my current scope and EPs very well, which makes me want to upgrade to something that will take me years to go around.

The versatility of the f/8 6" Celestron and the extensivity of the goto, plus the option to play with photography on some occasions is neat. Worst case scenario it probably will keep decent resale value...

I have been considering other 150mm scopes and mounts, different budgets and all, but I kept coming back to the VX6 at the end of every turn.
I'm aiming for an early 2023 purchase, if nothing changes my mind by then. And unless some manufacturer release a compatible pier in the next few months I will probably post the DIY pier with photos on CloudyNights.

It is always such a plus to see other astronomers post their rigs and gear!

Thank you everyone on this thread for those btw!

#30 DeanD

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Posted 15 August 2022 - 07:48 PM

Good luck, and I am sure something will come up eventually: I got a lot of my equipment in the much smaller Aussie "used" market. BTW, the extension you can see on my M2 mount is home-made, as is the tripod. Just for fun, here is a "before" and "after" image of a 90mm f10 scope that was originally used by the legendary comet hunter Bill Bradfield. I thought it could do with a make-over...  wink.gif The "after" is in post #32

 

Before:

 

Bill Bradfield 90mm 1.jpg

 

Complete with lens cover:

 

Bill Bradfield 90mm 2.jpg


Edited by DeanD, 15 August 2022 - 07:56 PM.

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#31 Echolight

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Posted 15 August 2022 - 07:52 PM

Can I ask you about that mount? 

Since it's alt/az how do you operate micro adjustments? I don't see slowmo knobs...

No slow motion. But it’s very smooth. I just guide it around with one finger on the diagonal.

 

And it’s super easy to set up. Just slips on the yoke on top of the tripod.

6981671C-9EDB-4259-BFA3-2DD1BE56C45D.jpeg

 

Very tall. And not too heavy. I really love this scope and mount.

EEA1675B-06BE-4334-B441-D2CA4FF9D55F.jpeg


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#32 DeanD

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Posted 15 August 2022 - 07:55 PM

And this is its new iteration:

 

 

Bill Bradfield 90mm refurbished small copy.jpg

 

 


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#33 Astroyesmer

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Posted 15 August 2022 - 08:05 PM

No slow motion. But it’s very smooth. I just guide it around with one finger on the diagonal.

 

And it’s super easy to set up. Just slips on the yoke on top of the tripod.

attachicon.gif6981671C-9EDB-4259-BFA3-2DD1BE56C45D.jpeg

 

Very tall. And not too heavy. I really love this scope and mount.

attachicon.gifEEA1675B-06BE-4334-B441-D2CA4FF9D55F.jpeg

  1. Looks perfect... Did you or do you ever feel like changing the focuser? Or does it just do the job fine?

 

And this is its new iteration:

 

 

attachicon.gifBill Bradfield 90mm refurbished small copy.jpg

That's a neat job. Hopefully I will manage to do something as clean!


Edited by Astroyesmer, 15 August 2022 - 08:08 PM.


#34 Echolight

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Posted 15 August 2022 - 08:20 PM

Can I throw a spanner in the works? I have a TSA102, which satisfies my desire for optical near-perfection, and a Celestron 150 f5 achromat. I think they complement each other nicely: I didn't get the Celestron for high power views, although it does surprisingly well on the planets up to around 120x, except for Mars. A Baader "fringe killer" filter does a good job on the planets too: and I have read that their "Contrast booster" filter is even better.

 

The f5 achro is not my instrument of choice for viewing bright stars or high powers on the planets (that would be the TSA102), but it excels in wide-field, deep sky views, especially of extended nebulae and galaxies. At low power in a head-to-head one night I found I could tell very little difference on galaxies and nebulae between it and both a Skywatcher Evostar ED 150 and their "true" apo, the 150 Esprit triplet. (Actually there was a difference: the f5 achro showed a wider field!) the reason I did the "head-to-head" was the owner wanted to sell his Evostar and keep his Esprit. The Evostar is an amazingly good scope for the money (especially the money he was asking), but I found it surprisingly easy to resist temptation and simply keep my f5...

 

I have even gone from observing the "homunculus" and the surrounding nebula of Eta Carina through a 24" dob and back to my f5 achro using a "deep sky" filter, and not feeling disappointed.

 

The bonus with the f5 is that it doesn't require a big mount, in fact it is quite happy on the Stellarview M2 (see below) and an old iOptron MiniTower (the same mounts I use for the TSA102). It only weighs around 7.2kg (vs 5.4 for the Tak), and it is about the same length as the Tak. It doesn't feel like a big telescope (I have looked through a 8" f12 refractor: that was a big telescope!), and I can easily carry it one-handed.

 

Unfortunately it doesn't seem to be available new anymore: but I would keep my eye out for a used one if I were you (that's what I did!). (PS: Skywatcher may still make them: eg. see https://www.teleskop...tml?language=en  or Kson: https://www.astrodog...ar-sweeper-ap/)

 

attachicon.gif2018-02-02 16.51.30.jpg

 

I know the often referenced table in one of the above posts shows "unacceptable" CA for a 150mm f5 scope, but I think this is a quite subjective view, and it certainly doesn't fit with my experience. The 102mm f8 "Super Apo" and the 150mm f5 achro are for me a winning combination.

 

And, as for a 5" or a 6" aperture upgrade: go the 6": it provides images of more than twice the brightness than a 4", and this is very noticeable on DSO's, even when compared to a top-of-the-heap 4".

 

All the best,

 

Dean

I almost bought one of these... but didn’t. The low weight is a really nice feature. But I already had the f/8. So I couldn’t decide and then it was gone. 
 

Lately I’ve been contemplating the f5.9 Altair Starwave 152. It’s a bit heavier with it’s sliding dew shield and 2.5 inch 2-speed rack and pinion focuser. About the same weight as my f/8 I believe.

https://www.altairas...scope-461-p.asp

Should get 2.9 degrees and 6.8mm exit pupil at 22x with an XW40. Although 3.1 degrees and 5.6mm exit pupil at 27x with the 28 PWA in the f5 might’ve been a bit nicer, I figure the Starwave 152 might be a little better at higher power.


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#35 Echolight

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Posted 15 August 2022 - 08:31 PM

 

  1. Looks perfect... Did you or do you ever feel like changing the focuser? Or does it just do the job fine?

 

That's a neat job. Hopefully I will manage to do something as clean!

 

I’m ok with the focuser. At f8 the single speed isn’t too hard to get really sharp focus. And I don’t particularly like Crayford focusers. A 2-speed rack and pinion seems like a considerable expense. So I’ll just continue to use it like it is.

 

Many people will scoff at the idea with a fast achromat, but the scope aint too bad at 360x on the terminator of the Moon. And focusing isn’t too much of a chalkenge.


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#36 Astroyesmer

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Posted 16 August 2022 - 01:04 AM

Not that I already think of replacing it, was just wondering. The focuser on my cheap 4" is a bit rough on the edges and the shake at high mag doesn't help but I really ended up getting a hand and an eye for it... I can't imagine how a breath of fresh air a sturdy mount and a f/8 focus will feel!



#37 Thomas_M44

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Posted 16 August 2022 - 12:17 PM

Hi friends

 

I have a fairly specific question, not really aiming for any advice like "you better get a 8 inch dob" or "this and that is easier to carry and cheaper" etc:

 

I would just like to know, from a realistic perspective, at equal night sky and equal user experience, observing same objects, how dramatic is it to move from a 4" f/6.5 to a 6" f/8?

 

And a bonus inquiry for the scopes hoarders that own many rigs:

 

What about a 5" f/8 achro inbetween those two?

 

Let's keep the conversation about what happens through the eyepiece and disregard logistics please! (Visual observation only) laugh.gif

If you’ve got the money for a 5-inch f/8 achromat, IMO you’re far better off getting an 8-inch f/6 Newtonian.

 

As much as I have a soft spot for 6-inch Newtonians, if you already have a 4-inch refractor, the move to an 8-inch Newtonian would give you a much more decisive step up with appreciable brightness gain.

 

The step from a 4-inch refractor to a 6-inch Newtonian really won’t be that impressive beyond the lack of Chromatic Aberration in the Newtonian, particularly at higher magnifications. A decent 8-inch however, would represent solid performance gains.

 

Any eyepieces you already have which work well with your f/6.5 achromat, they would also work well with an f/6 Newtonian.

 

I’d suggest also keeping the 4-inch f/6.5 primarily for it’s low magnification/ wide-field capabilities with 2-inch eyepieces.
 

A 4-inch refractor plus an 8-inch Newtonian IMO are highly complimentary, and make a great team waytogo.gif 

 

I’d skip the 5-inch f/8 Achromat. It’s really just not going to add much beyond the capability you already have with the 4-inch f/6.5.


Edited by Thomas_M44, 16 August 2022 - 12:20 PM.

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#38 Astroyesmer

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Posted 16 August 2022 - 12:54 PM

Oh I will keep that little 4" forever, it's the perfect grab'n'go travel buddy!

But I have put eyes in many telescopes of different types and sizes, and I really really don't feel the appeal of newtonians under massive aperture such as 14 or 16 or so.

I am definetly a refractor guy and feel it will probably stay that way. This thread helped me decide I will ditch the 5" achro idea and go for a 6".
I can deal with CA and there are efficient enough hacks to get rid of it so I don't even dig apos. Of course if I win the lotery I will end up with a 230mm Tak refractor on a robotized crane with the whole ES and Televue range of collections but until then the 6" Celestron witll be my ride!

The only thing I would eventually add to a couple refractor is a beefy 4" binocular set, but it seems manufacturers can still improve on those.

#39 John Huntley

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Posted 16 August 2022 - 01:05 PM

I hope you enjoy your 6 inch F/8 achromat when you get it. I've owned a few over the years and had some fun with them. I didn't pay much for them though - a round $200 (unmounted) was the most I think. 

 

After using a Chromacor CA / SA corrector with them I realised what an ED doublet could do so that's what I moved onto when I had the chance. 

 

I love refractors but my 12 inch dobsonian has given me the most "wow !'s" and "firsts" over the years so I consider that my best scope smile.gif


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#40 Astroyesmer

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Posted 16 August 2022 - 01:29 PM

My neighbor owns a 12" dob, so we can enjoy both together :D

 

I will check the chromacor, have no idea what it is thanks!



#41 John Huntley

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Posted 16 August 2022 - 01:58 PM

 

I will check the chromacor, have no idea what it is thanks!

https://www.cloudyni...3814-chromacor/
 



#42 Echolight

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Posted 16 August 2022 - 05:04 PM

Not that I already think of replacing it, was just wondering. The focuser on my cheap 4" is a bit rough on the edges and the shake at high mag doesn't help but I really ended up getting a hand and an eye for it... I can't imagine how a breath of fresh air a sturdy mount and a f/8 focus will feel!

Those 4 inch f6.5 scopes don’t usually come with a very beefy mount and tripod. And of course the shorter the focal ratio, the less your depth of focus will be.



#43 Echolight

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Posted 16 August 2022 - 05:05 PM

I will check the chromacor, have no idea what it is thanks!

You won’t likely find one. And if you do it’ll probably cost a thousand dollars.

 

Just because some people believe it’s a necessity doesn’t mean it is for everyone. It’s funny how so many make out like your not allowed to look at planets or the Moon with a fast achromat. Yet there are lots of people who do and enjoy the view.

They’ll say get a dob. And then half the people who do either don’t want to collimate it or just make it worse when they try. And you end up with a bunch of folk who think this is as good as it gets and never ever get a crisp clear high power view of the Moon or planets. Then half of those dobs end up collecting cobwebs in a shed or garage.
But oh no! Don’t use an achromat to look at the Moon or Jupiter! You’ll burn in hell... or feel the wrath of the purists lol.gif


Edited by Echolight, 16 August 2022 - 05:16 PM.

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#44 Jeff B

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Posted 16 August 2022 - 08:40 PM

Did someone say/type Chromacor?

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#45 Astroyesmer

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Posted 16 August 2022 - 11:53 PM

You won’t likely find one. And if you do it’ll probably cost a thousand dollars.

Just because some people believe it’s a necessity doesn’t mean it is for everyone. It’s funny how so many make out like your not allowed to look at planets or the Moon with a fast achromat. Yet there are lots of people who do and enjoy the view.
They’ll say get a dob. And then half the people who do either don’t want to collimate it or just make it worse when they try. And you end up with a bunch of folk who think this is as good as it gets and never ever get a crisp clear high power view of the Moon or planets. Then half of those dobs end up collecting cobwebs in a shed or garage.
But oh no! Don’t use an achromat to look at the Moon or Jupiter! You’ll burn in hell... or feel the wrath of the purists lol.gif


I meant check it on google to learn what it is... I personally don't have a problem with CA, since I don't do astrophoto. And for visual observers, aside from the moon and Jupiter it really isn't that big of a deal in my opinion. But to each their own! Maybe in a near future apos will go cheaper anyway!

 

Also if I burn in hell from watching the moon with an achro, will the flames purifying my soul be legit orange or spoiled by a purple haze??

 

(Edit: typos)


Edited by Astroyesmer, 17 August 2022 - 04:17 PM.

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#46 Jeff B

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Posted 17 August 2022 - 07:42 AM

I meant check it on google to learn what it is... I personally don't have a problem with CA, since I don't do astrophoto. And for visual observers, aside from the moon and Jupiter it really isn't that big of a deal in my opinion. But to each their own! Maybe in a near future apos will go cheaper anyway!

 

Also if I burn in hell from watching the moon with an achro, will the flames purifyong my soul be legit orange or spoiled by a putple haze??

Totally.

 

Actual, based upon the samples I've measured as well as other achromats sourced from the east, best correction is in the yellow/red so the orange flame purity is just fine.  


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