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Let's talk about diagonals...

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#51 nicoledoula

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Posted 10 November 2019 - 05:49 PM

More light comes through with no diagonal, It'\s why most Japanese view straight through.  And Mr Jones your opinion on previous tasting didn't bother me at all. all opinions are welcome IMO.


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#52 Kiriakos_GR

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Posted 10 November 2019 - 06:20 PM

More light comes through with no diagonal, It'\s why most Japanese view straight through.  And Mr Jones your opinion on previous tasting didn't bother me at all. all opinions are welcome IMO.

I do not disagree but refractors they are excluded. 

There is no chance looking to zenith with out diagonal.

In the end of the day the diagonal is add-on accessory, a tool this offering convenience.



#53 MrJones

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Posted 11 November 2019 - 10:01 AM

What I found in my own testing with SCTs is that the diagonals while important don't seem to have as much impact as they can on refractors. In other words the differences between diagonals was more easily seen in refractors than SCTs. Being a refractor owner and testing the Celestron and Meade SCT diagonals I sold them off and just used a 2" AP Maxbright with my SCTs which was much better aligned and had lower scatter in my diagonal testing. 

Agreed! Something about adding especially a mirror to a lens only system makes more of a visual difference (i.e. degradation) than adding a 3rd mirror. A straight through refractor is really fun if fairly impractical for most of us.

 

D/F = 2 tan( sin-1(n sin(45o - thetaC))

 

From this I get that - on axis - a BaK4 prism is usable to f/3.35 and BK7 is usable to f/5.01. This suggests that neither should exhibit issues with the critical angle when used at sensible telescope f-ratios.

f/10 for BK7 and f/6.7 for BaK4 as per my post above.


Edited by MrJones, 11 November 2019 - 10:02 AM.

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#54 YAOG

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Posted 11 November 2019 - 01:29 PM

Agreed! Something about adding especially a mirror to a lens only system makes more of a visual difference (i.e. degradation) than adding a 3rd mirror. A straight through refractor is really fun if fairly impractical for most of us.

<< SNIPPED >>

All you need are some friends to help stand you on your head, then the horizon is moving up! Then diagonal-less refractor observing is 100% natural. 



#55 Parsonsk

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Posted 08 September 2020 - 08:00 PM

It's been awhile since anyone posted on this one but as a newb, I'm wondering if I would see a noticeable difference between the stock diagonal on my evolution 6 and an upgraded Celestron Star dielectric diagonal (I think the answer here is yes but how much)  and then again would I see a difference from the Celestron to the Televue everbrite?

 

thanks


Edited by Parsonsk, 08 September 2020 - 08:02 PM.


#56 Peter Besenbruch

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Posted 08 September 2020 - 08:53 PM

If Celestron supplies a 1.25" prism diagonal, going to a dielectric will get you slightly brighter images, and noticeably more scatter. If your diagonal has an aluminized mirror, then again, the dielectric will be a bit brighter. Celestron diagonals tend to be misaligned. If you can check and align the diagonal, you should be good with what you have.

 

In general, be careful switching to a system that can accommodate 2" accessories. You have a fairly light, compact scope, and going 2" will mess that up.



#57 Kiriakos_GR

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Posted 09 September 2020 - 02:12 AM

It's been awhile since anyone posted on this one but as a newb, I'm wondering if I would see a noticeable difference between the stock diagonal on my evolution 6 and an upgraded Celestron Star dielectric diagonal (I think the answer here is yes but how much)  and then again would I see a difference from the Celestron to the Televue everbrite?

 

thanks

You may get in to such comparisons only if you have a truly well performing eyepiece.

I decided to get out of the game, because I am in denial to pay over 30 Euro about it.



#58 monoceros

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Posted 09 September 2020 - 11:15 AM

I've searched CL forums and learned some things about diagonals, but there is not a lot out there.  And it seems diagonals are kind of an important and necessary component. Still, while there are a lot of offerings in the marketplace there doesn't seem a whole lot of discussion.  So, can we have a discussion about diagonals?

 

For background, I'm a Dob guy.  Or at least that's the only telescope I've ever owner until now.  Diagonals were unnecessary for me as I never laid my Dob down low enough to need one.  But, I now have a 4" refractor (102mm, f/7) coming.  I plan on using it for a family trip next year to some areas with dark skies (NV/UT/AZ triangle).  It doesn't come with a diagonal.  While planning/buidling a travel mount/tripod, I got a deal on a Meade LX65 mount where the 5" Mak is basically being thrown-in.  For ****-and-giggles I'll see what it can do...and at an f/15 (1900mm) I'm thinking it is best suited for high-power EP's and thus might want to upgrade the stock 1.25" diagonal.  

 

So far it seems for a 2" diagonal for the refractor I'm best served buying the highest priced diagonal I can afford.  I know about dialectic coatings.  I've learned quartz is good too.  I can figure out 1/10 v 1/12 wave (although is it really that simple: .1 v .0833?).  But what is a star diagonal?  Is there a diamond or asterisk diagonal?  Are there different types of diagonals (beyond their mirror materials and polishing)?  Not a lot of variety in design in those things.  Also, why doesn't anyone care about weight of these things?  Seems hardly anybody gives the weight of diagonals yet people fret about the heft of their Nagler 31mm EP as throwing off balance and/or crossing the weight threshold on their mount.  Seems a diagonal made of light-weight unobtanium would help mitigate against EP weight ... yet this is a very intelligent hobby so if weights are not given as a matter of course then what am I missing?

 

For 1.25" diagonals I read even more chatter.  Like prisms might be better?  I believe that is due to the idea 1.25" diagonals are more common on scopes which might be used more often for terrestrial viewing?  But I have also read once or twice that people suggest prism diagonals might be used to reduce coma or achieve a flatter image?  Since comments like those were rare and since I don't seenany 2" diagonals being prisms then I'm doubtful ... but my mind could contemplate a prism being used to address visual issues like those?  Also, if prisms aren't as optically beneficial as mirror diagonals, then why do Takahashi and Baader offer prism 1.25" diagonals - and not cheaply?  And, in speaking of prisms, why an Amici prism where others don't indicate Amici?  Do Tiesto and Diplo also have prisms?  And, why does it seem every 45 degree, 1.25" diagonal is a prism but not as many 90 degree prisms...the terrestrial viewing thing again?

 

So, chime in with your diagonal knowledge.  Might be a nice break from all the EP talk....

That Celestron diagonal looks like a genuine bargain at $15 a pop.  The specs are reasonable and are ideal for those who suffering during this danmed pandemic.


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#59 Procyon

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Posted 09 September 2020 - 01:32 PM

I measured a bunch of new and used commercial Star Diagonals a few years ago, and indeed, the Astrophysics, TeleVue and Lumicon came out on top, also the Celestron classic 1.25 prismatic was great. The others were all over the map, some ab-used ones, but also some new BNIB ones!

 

I'd have reasonable confidence in the premium brands, BNIB, from dealer... and would "pay-up" for that assurance...

 

Here's the summary sheet from my study... my measurements were very accurate, but my selection includes a lot of used ones.   Tom

Awesome info Tomdey thanks. Would have been nice to have one column with the total lightpath or clear aperture in mm. Some peeps can get a diagonal with say 39mm aperture than complain when they try an eyepiece with a wide field stop like the 40mm Pentax XW lol.

 

I wonder how the Baader 2" Clicklock Dielectric would perform.

 

post-226662-0-80939100-1572321180.jpg


Edited by Procyon, 09 September 2020 - 01:42 PM.

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#60 TOMDEY

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Posted 09 September 2020 - 01:45 PM

Awesome info Tomdey thanks. Would have been nice to have one column with the total lightpath or clear aperture in mm. Some peeps can get a diagonal with say 39mm aperture than complain when they try say a 40mm Pentax XW lol.

 

attachicon.gifpost-226662-0-80939100-1572321180.jpg

I measured that stuff too. The aperture and light path (twixt the front and back openings) that relates to vignetting. Just not displayed in the table. One really needs a three-inch Star Diagonal to enjoy vignetting-free presentation when using ... Ummm... here's a related picture...  Tom

 

~click on~ >>>

Attached Thumbnails

  • 79 three-inch focuser and Star Diagonal annotated.jpg

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#61 bulletdodger

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Posted 12 September 2020 - 01:07 PM

    I have read hundreds of threads on diagonals over the years as well as my own experiences. Only the most discerning of observers will ever see a difference between a a quality diagonal costing 50-100 dollars and a Super quality one costing 250-500

dollars. Even the very lowest price ones can throw up a pretty decent view. 

      The telescope and eyepiece are much more important in the equation. More important to me is the construction of the diagonal. The TV diagonal's use the same bodies in all their 2 inch versions. They are one piece which means they won't come unscrewed at an inopportune time casting your 600.00 Ethos to the ground. 

 

Bob


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#62 SteveG

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Posted 12 September 2020 - 01:21 PM

    I have read hundreds of threads on diagonals over the years as well as my own experiences. Only the most discerning of observers will ever see a difference between a a quality diagonal costing 50-100 dollars and a Super quality one costing 250-500

dollars. Even the very lowest price ones can throw up a pretty decent view. 

      The telescope and eyepiece are much more important in the equation. More important to me is the construction of the diagonal. The TV diagonal's use the same bodies in all their 2 inch versions. They are one piece which means they won't come unscrewed at an inopportune time casting your 600.00 Ethos to the ground. 

 

Bob

I completely agree with your first comment. It takes very good seeing to discern a difference in 2 diagonals. I've had only one night of seeing that good this year.

 

I'm sure the TV construction and optics are excellent, but I've never had a diagonal "unscrew" under the weight of heavy eyepieces. In my refractors, the weak point would be the compression fitting at the visual back.



#63 sanbai

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Posted 12 September 2020 - 04:24 PM

I have read hundreds of threads on diagonals over the years as well as my own experiences. Only the most discerning of observers will ever see a difference between a a quality diagonal costing 50-100 dollars and a Super quality one costing 250-500
dollars. Even the very lowest price ones can throw up a pretty decent view.
The telescope and eyepiece are much more important in the equation. More important to me is the construction of the diagonal. The TV diagonal's use the same bodies in all their 2 inch versions. They are one piece which means they won't come unscrewed at an inopportune time casting your 600.00 Ethos to the ground.

Bob

I have two different diagonals in the "expensive" group: the BBHS mirror and prism. I could only compare them to the stock 1.25 celestron prism and 2" Sky-watcher. I haven't been able to see the difference. My testing wasn't exhaustive and I'm definitely not the most critical observer, though. So yes, I share your opinion. I like to compare things, but certainly have better things to do when I'm (able to be) observing.

I hope they do perform better on certain critical conditions I may face one day. People have reported advantages. The good thing is that I know I don't need put more money in an upgrade, and I like a lot the clicklock!

#64 Thomas_M44

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Posted 12 September 2020 - 06:00 PM

There is nothing intrinsically 'wrong' with using a quality BK-7 glass in an astronomical prism.

 

Assuming good optical quality, good coatings, suitable f-ratio match with the telescope and so forth.

 

BaK4 = GOOD, BK-7 = BAD:  this is simply an erroneous oversimplification


Edited by Thomas_M44, 12 September 2020 - 06:01 PM.

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#65 25585

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Posted 13 September 2020 - 07:47 AM

My money went on Baader's astro quality Amici. It is my single most expensive optic to date. But it gets used enough to justify its price. It has BBHS coating and a Clicklock eyepiece grabber, so 3 in 1 good qualities.

 

Thing is, to spend on great scope optics, compromising on an important part of your optical train makes no sense. Eyepieces can be chopped & changed, but diagonals are IMO equally or more important.


Edited by 25585, 13 September 2020 - 07:49 AM.

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#66 Scott99

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Posted 13 September 2020 - 11:17 AM

just remember one simple metric - 1% per inch of glass.  That's the approximate light loss of even the best prism diagonals.   So 1.25" inch prism about 1% loss from light path, T2 diagonals about 2%, and full 2-inch prisms 4% light loss.  In addition to any light reflected from hitting the coatings on the glass.

 

This is the reason that prism diagonals were traditionally offered in 1.25" size and mirror diagonals in 2-inch size.   Amici diagonals are nice but you can look inside and see a dark line running up & down the split in the prism...it doesn't take much imagination to figure out what that's going to do to your image quality.


Edited by Scott99, 13 September 2020 - 11:20 AM.

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#67 bulletdodger

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Posted 13 September 2020 - 12:21 PM

I have realized my diagonal was on the edge of coming unscrewed on more than one occasion. Even after tightening the shaft to the body as tight as I could it was suprising the small amount of pressure it takes to unscrew it. Now combine that with someone accidentally hitting it with their hand. I began to use teflon tape to give the threads more grip to make it tighter.
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#68 R.Kelley

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Posted 13 September 2020 - 12:45 PM

I measured a bunch of new and used commercial Star Diagonals a few years ago, and indeed, the Astrophysics, TeleVue and Lumicon came out on top, also the Celestron classic 1.25 prismatic was great. The others were all over the map, some ab-used ones, but also some new BNIB ones!

 

I'd have reasonable confidence in the premium brands, BNIB, from dealer... and would "pay-up" for that assurance...

 

Here's the summary sheet from my study... my measurements were very accurate, but my selection includes a lot of used ones.   Tom

https://www.cloudyni...-1572321180.jpg

 

Hi Tom. Question about your chart [which is very informative by the way waytogo.gif]. What data is being measured in columns 4 & 5? 



#69 25585

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Posted 13 September 2020 - 01:20 PM

just remember one simple metric - 1% per inch of glass.  That's the approximate light loss of even the best prism diagonals.   So 1.25" inch prism about 1% loss from light path, T2 diagonals about 2%, and full 2-inch prisms 4% light loss.  In addition to any light reflected from hitting the coatings on the glass.

 

This is the reason that prism diagonals were traditionally offered in 1.25" size and mirror diagonals in 2-inch size.   Amici diagonals are nice but you can look inside and see a dark line running up & down the split in the prism...it doesn't take much imagination to figure out what that's going to do to your image quality.

The Baader BBHS Amici has no issues for visual. My APM not quite so good, but acceptable. For imaging and NV devices, dunno.

 

If I bought a T2, it would be a BBHS mirror or prism.


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#70 TOMDEY

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Posted 13 September 2020 - 03:13 PM

https://www.cloudyni...-1572321180.jpg

 

Hi Tom. Question about your chart [which is very informative by the way waytogo.gif]. What data is being measured in columns 4 & 5? 

That's the angular and lateral misalignments of the input vs output tubes, as imaged by the mirror or prism inside. Here's one of the pages from the white-paper that gets into that kinda stuff >>>    Tom

 

~click on~ >>>

Attached Thumbnails

  • 112 star diagonals tom paper p9.jpg

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#71 letterman7

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Posted 15 October 2020 - 10:04 AM

Hi all,

Older thread by a month, and a newcomer here. I've just purchased a used, but in decent shape, Celestron Celestar 8, the basic unit. After doing a straight-thru collimation and got it as near perfect as possible, I put on the (apparently) supplied Celestron marked diagonal and had to "re-collimate" to that. It seems that any slightest touch on that diagonal throws the entire thing off, and I see no logical way to actually "tighten" the diagonal to where it won't move even a fraction in the mount. So, after reading through this thread and the supplied links to other threads (specifically, the comparison page) I'm more confused than ever on what direction to go. I know I probably should upgrade the diagonal since it obviously isn't as solid as it should be, but what might be a next logical step? I don't do terrestrial viewing with it, mostly star and planet hopping. I'd love to think I could do DSO's but I don't think the 8" is large enough with the amount of light pollution we have in my area.

 

Insights?

Thanks,

Rick



#72 Starman1

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Posted 15 October 2020 - 01:33 PM

Hi all,

Older thread by a month, and a newcomer here. I've just purchased a used, but in decent shape, Celestron Celestar 8, the basic unit. After doing a straight-thru collimation and got it as near perfect as possible, I put on the (apparently) supplied Celestron marked diagonal and had to "re-collimate" to that. It seems that any slightest touch on that diagonal throws the entire thing off, and I see no logical way to actually "tighten" the diagonal to where it won't move even a fraction in the mount. So, after reading through this thread and the supplied links to other threads (specifically, the comparison page) I'm more confused than ever on what direction to go. I know I probably should upgrade the diagonal since it obviously isn't as solid as it should be, but what might be a next logical step? I don't do terrestrial viewing with it, mostly star and planet hopping. I'd love to think I could do DSO's but I don't think the 8" is large enough with the amount of light pollution we have in my area.

 

Insights?

Thanks,

Rick

I live in LA, and I "know" light pollution--he is a friend of mine who lives here.

an 8" in a city can see:

--Moon

--Planets

--Carbon stars

--double stars

--bright open star clusters (use magnifications well above 100x to darken the background sky)

--bright globular star clusters

--the brightest asteroids

--occasional bright comet

--the very brightest nebulae (with a nebula filter)

That will give you thousands of things to view.

 

What should wait for a trip to dark skies are:

--nebulae (planetary, bright, dark, reflection, WR excitation, supernova remnants)

--galaxies

--faint star clusters (open or globular)

--Pluto

--faint telescopic comets

 

You may want to see the dark sky targets in the city, but you will be disappointed unless you live at the periphery of a very small city.

But I think if you tried, you just might find that the objects I list above that are visible in a city will be worth tracking down.


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#73 BillP

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Posted 15 October 2020 - 02:32 PM

For background, I'm a Dob guy.  Or at least that's the only telescope I've ever owner until now.  Diagonals were unnecessary for me as I never laid my Dob down low enough to need one.  But, I now have a 4" refractor (102mm, f/7) coming.  I plan on using it for a family trip next year to some areas with dark skies (NV/UT/AZ triangle). 

Hi Curt.  Diagonals are a link in the optical chain, so as critical as the secondary on your Dob.  If the secondary had wavefront error or not high reflectivity, does not matter how good your primary mirror is.  Same goes for the diagonal in a refractor.

 

Here's some things to chew on...

 

1. Diagonals come in 2" and 1.25" primarily, so choose the size commensurate with the largest eyepiece you use.  Also remember for travel the 2" is heavier and takes up more room.  You need to be careful also relative to how much focuser travel your refractor has because I have had occasion, like with an 80mm f/6 I used to have, that a 1.25" diagonal could not be racked out far enough to come to focus with a 25mm and 30mm Plossl I was using.  Since the light path of a 1.25" diagonal is smaller it means you will have to rack out the focuser more to come to focus.  One way to get around all this is with the Baader T2 Zeiss-spec 1.25" Prism diagonal.  I configure mine with a 2" nosepiece and have both 2" and 1.25" eyepiece holders.  Since it has a relatively large 34mm clear aperture, it works fine with no visual vignetting using 2" eyepiece up to 36mm field stops (e.g., my 30XW).  Then being a high quality prism it has superb contrast and definition so is wonderful for high magnification planetary too and has a very short light path if using a binoviewer and wanting to try to be able to do that without needing an OCA/GPC or Barlow to get to focus.

 

2. Common technologies are: Dielectric, BK4 Prism (best all around for any focal ratio), BK7 Prism (fine as long as the focal ratio of the scope is >f/4 otherwise will vignette I understand), Aluminized Glass Mirror, Silvered Glass Mirror, Gold coated glass Mirror (the latter rare - VERNONscope).  Dielectrics are most common these days, and run of the mill ones have noticeably more scatter that the premiums.  Prisms generally least scatter.  Aluminum/Silver/Gold mirrors, like all mirrors, will have more scatter as is the nature of the beast.  Not a lot of aluminum/silver/gold mirrors these days either.  Taks has a aluminum mirror diagonal, Baader has a Silver one (excellent), and VERNONscope has Silver and used to have Gold as well (both excellent and best I have looked thru of any diagonal but mighty pricey).  Aluminum and Silver coatings can deteriorate over time, just like a primary mirror does on your Dob.  But the modern ones are overcoated well so have not heard of any deterioration from anyone I know that has them over a decade and more.  Baader claims theirs will last at least 30 years I believe (can't recall exactly). 

 

3. Coatings - used vintage ones can have single coatings so look out for those, non-specified multicoatings, and Baader has a proprietary coating called BBHS.

 

4. You need to be careful on wavefront claims.  Most state they are prior to coating or they do not state.  Problem there is if there is any wavefront error on the glass substrate then it will get amplified with each layer of coating.  Not so big of a deal when aluminized and just putting an enhanced coating to protect.  But it a dielectric well those have 40 or more layers so an OK wavefront on the glass can be magnified to not so hot after 40 coats!  Some manufacturers do though specify after coating which is good.

 

5. Thermal Issues - There are various claims for the glass types used.  Some taught zero expansion glasses.  IMO though given how small the glass is in the first place, I do not think those issues are worth worrying about.  But then again it cannot hurt..except in the wallet.  Most all diagonal technologies will show astigmatism, even on-axis, for the first 5-15 minutes when going from warm inside to very cold outside.  Dielectrics seem to be the worst here for that in my testing, my assumption is because of the differential stresses as each of those 40 layers expand and contract.  But they all settle to no issues after 15 minutes.  Prism are the least affected in my testing.

 

6. Eyepiece Holders - The typical is just compression ring, but some you can get with locking collets that you rotate, like the Baader Clicklock.  Some people like that method, others don't.  The ones I have seen do add weight though so consider that when making a choice.  I have both type and tend to like compression rings as simpler and what I am used to.

 

7. Cleaning - they all accumulate dust over time so cleaning is a must.  Dielectrics are rock hard so clean them with any cloth you like.  aluminum/silver/gold mirrors range from fragile to tough depending on the coatings used on them.  Some have 4 layer multicoats which are harder than standard primary mirror coatings, in any event more care with these just like you are used to with your Dob mirror.  I have the Baader Silver and it has several layer multicoat protecting it.  I find it not fragile.  Prisms are just glass that are similarly multicoated.  Care required by not as fragile as your Dob mirror.  So pretty hard IME and just like the glass on your eyepiece and refractor objective.  So if you cannot take care of your eyepiece, then recommend don't get a refractor or a prism, and maybe get out of the hobby as all your eyepiece will become trash lol.gif  Moral of the story, use reasonable skill and care and they will last generations!  I have some 40+ year old prisms and they are just fine after all this time.

 

8 - My preferences - I have shied away from Dielectrics after that testing review I did.  In direct compares to other technologies they had views generally with more scatter and less vibrant colors.  The premiums from Baader, AP, and TV though definitely had the least scatter of Dielectrics.  Not as good as the Prisms, but close enough.  The Prisms though generally showed to my eye a more color saturated and contrast saturated view.  For planetary I found them easily preferable to Dielectrics.  The Silver mirrors accentuate the reds to my eye, so they make carbon stars and the GRS viewing more fun.  Also extremely bright appearing views.  Looking for very faintest stars the Baader BBHS showed better here than any of the others, with Prisms hot on its heels.  But this advantage IMO would only be worth it if you are a glob core resolver or something.  So wanting to pursue the faintest stars always.  If most of what you do is lower magnification sweeping vista viewing or standard DSO viewing, any of the technologies is just fine.  So only when you are critical relative to scatter, color saturation, planetary performance do the differences really become important IMO.  The diagonals I maintain are the Baader T2 Zeiss Prism in 2" and 1.25", a Baader BBHS Silver Mirror, and an APM 1/12th wave Dielectric.  The latter I use for knock around and travel as I prefer to leave my expensive stuff safe at home. Good for what it is even though not a premium.

 

9 - View Orientation - One last thing...the Star Diagonal is simply a standard diagonal and the view will be correct up and down but reversed from normal left to right.  There are "erect view" or "right view" diagonals, Amici is one of these types, that show everything normal in orientation just like binoculars.  These are good if you intend on doing daytime spotting.  The premiums for high magnification astronomy are way expensive, then the others are the common versions that are basically economy.  I have one of the cheapie 1.25" ones from Astromania.  I think it is $35.  Fun and works great and handy to have if planning on taking the refractor out for some terrestrial observing.

 

10 - Others have referenced my review so you already have that link.  It was an eye opening experience for me when I did it as I never really considered the diagonal an overly important component.  But after the side-by-sides and my passion for planetary it became obvious that the different technologies do indeed matter.  So do not take this component for granted if you are a critical observer and demand superlative performance from your equipment.  If you are more a casual observer mostly out for fun then the views are great through any ole diagonal so get one with a descent build and have at it.


Edited by BillP, 15 October 2020 - 02:32 PM.

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#74 letterman7

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Posted 15 October 2020 - 03:01 PM

I live in LA, and I "know" light pollution--he is a friend of mine who lives here.

an 8" in a city can see:

--Moon

--Planets

--Carbon stars

--double stars

--bright open star clusters (use magnifications well above 100x to darken the background sky)

--bright globular star clusters

--the brightest asteroids

--occasional bright comet

--the very brightest nebulae (with a nebula filter)

That will give you thousands of things to view.

 

What should wait for a trip to dark skies are:

--nebulae (planetary, bright, dark, reflection, WR excitation, supernova remnants)

--galaxies

--faint star clusters (open or globular)

--Pluto

--faint telescopic comets

 

You may want to see the dark sky targets in the city, but you will be disappointed unless you live at the periphery of a very small city.

But I think if you tried, you just might find that the objects I list above that are visible in a city will be worth tracking down.

Thank you for that, Don. As I get further into evaluating the scope in general I'm hoping to be able to view much more than the "regular" objects most folks point to. Right now I have to sort the collimation issues that I'm having and it seems it's all pointing to the diagonal. It's one of those scopes that, depending on orientation, you can't just look "straight through" without some gymnastics and a younger body :-) Though, the next time I have it out I am going to have to check that view to make sure there isn't anything specifically wrong with the scope. I have bought one of those laser collimators and it seems to work well - it's just every time I move the scope I have to re-set it. The diagonal just exacerbates the issues. That said, do you have a suggestion on a logical step-up from the stock Celestron diagonal? I looked through your site.. nice stuff! Just wish I understood it more :-)


Edited by letterman7, 15 October 2020 - 03:20 PM.


#75 BillP

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Posted 15 October 2020 - 03:10 PM

10 - Others have referenced my review so you already have that link. ...

Curt,

 

BTW, nothing really new out there since my review in terms of the technology for the reflecting method.  It is not a part of the market that changes very much.  My review was just focusing on Star Diagonals, so not the Correct View types which people "generally" do not use for astronomy (Amici, Pentaprism, Erecting or Porro Prism).

 

Also, if you plan to image through the diagonal then not all the technologies pass all the spectrum (like UV and IR).  So if that is critical for you then get those details on the one you are selecting too. E.g., the Baader Dielectric reflects only the 400-700nm range, basically just visual, whereas as the BBHS Silver diagonal reflects 390-2000nm.  Here's a good overview of the different technologies, it is a Baader product manual, but goes over the basics for you, plus theirs have lots of connectivity options so more modular/flexible.  https://www.baader-p...s_t_2_and_2.pdf
 


Edited by BillP, 15 October 2020 - 03:22 PM.

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