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#51 Nicole Sharp

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Posted 26 November 2018 - 01:04 PM

The kits have a bunch of short focal length plossls that are of limited value.   I have the Celestron (or maybe its the Meade-branded one) zoom and its primary use for me is as a dust plug.  Other people like it though.  

 

I would not assume that eye relief stays constant when you use the zoom.  Plus it probably changes length (depending on how you mount the camera).   Parfocal eyepieces with constant eye relief will be different physical lengths as well.

 

You make a good point there about the eyerelief on the zoom.  I didn't think of that.  I would have to email Celestron about it, but I doubt it would remain constant either.



#52 Nicole Sharp

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Posted 26 November 2018 - 01:15 PM

A lot of these issues are why I want to get a prime-focus camera instead of an afocal camera.  But unfortunately that doesn't change the issue with balance when a Barlow is added.  If I wanted to use a Barlow, I would get a better performance from the telescope if I did the entire alignment with the Barlow already on the OTA.  But I would need a very good finderscope (probably something like a 9X50 or a StarSense) to do that, which adds more weight (the extra weight would probably be just as bad as the poor balance).  But I might be worried about nothing too.  I won't know if there will be tracking problems when using a Barlow until I actually try it.  I am sure lots of people align their telescopes without a Barlow, and then add a Barlow for planetary observing without going through the pain of rebalancing and realigning the entire telescope?


Edited by Nicole Sharp, 26 November 2018 - 01:16 PM.


#53 jallbery

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Posted 26 November 2018 - 02:02 PM

As long as you are in alt-az, you can't use exposures long enough that any tracking improvements from more precise alignment will make a difference.   At least I doubt that it will. The gears in the 5SE aren't as precise as they are for a mount designed for astrophotography.  Better alignment does not change that.

 

For visual use, the difference in weight between a couple plossls with or without a barlow isn't enough to seriously affect mount performance.  

 

I wouldn't try to use an SLR with a 5SE with a barlow.  Too much weight.  Too awkward.  Not enough mount clearance.  Stick to stuff you can shoot at prime focus at first-- don't make things harder for yourself.  If you want a little more magnification, crop the photo.   And the reducer will reduce the impact of tracking errors, even it does give you darkened corners.    For planetary, a 224 camera (or something similar) will be much better suited.


Edited by jallbery, 26 November 2018 - 02:05 PM.

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#54 jallbery

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Posted 26 November 2018 - 02:10 PM

You make a good point there about the eyerelief on the zoom.  I didn't think of that.  I would have to email Celestron about it, but I doubt it would remain constant either.

Or you could just google "celestron zoom eye relief", click on the celestron product page, click on specifications, and read that it is 15-18mm.



#55 photoracer18

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Posted 26 November 2018 - 06:00 PM

I am not that distant from Cumberland being in Martinsburg, WV. I have a lot of the things you are considering buying. If you wanted to meet at a star-party or something I could bring a lot of stuff you could try before shelling money out. I have about 7 DSLRs, 2 with modded sensors, a couple of one shot color cameras, a Nexstar 4se setup to carry other scopes like my 80mm TMB triplet and my LOMO Astele 95 MCT. Also have the Nexstar tripod with the built in wedge. Both 50mm and 80mm guidescopes, solar filters, solar diagonals,  a Coronado 40mm prominence setup for my SV102ABV (LOMO APO).

I did my first imaging with film in the early 60's using an RV-6 Newtonian, all lunar and planetary. But at 71 I don't do much imaging right now although I could

When it comes to eyepieces long eye relief has to be designed in. No Plossl has it because of the design as the amount is directly dependent on the focal length of the eyepiece. I have 2 sets of LER eyepieces, a full set of Pentax XLs from 5.2 to 40mm and a selection of smaller Vixen LV eyepieces I use for travel from 2.5 to 20mm. Also have a UO 55mm (2"). I have lots of 2" visual backs and 2" diagonals (both of which are somewhat overkill on a C5). I have owned 4 C5s although 3 of them were the rare 750mm telephoto version (F6). I personally think those are better by samples I have used than the F10 versions.

 

I also have a couple of cases for Nexstar 5 scope/mount I could sell you used if you want to see what they are like in person (one older and one newer).

I would also likely bring my AP400QMD mount on one of my tripods or piers (working on a LW tripod setup).

 

Big issue with using a Barlow for imaging is to remember that the exposure time goes down by a factor of the magnification of the Barlow. In the case of a TV 5x Powermate that means 5x shorter. Not as important when imaging bright objects, just dim ones. It also magnifies any optical issues and makes them worse by the same factor. I seldom use a Barlow except for my GTO 1.5x one (2"). Its actually the original prototype for what is now sold by Antares as their 1.6x Barlow.

 

Anyway if you have an interest PM me and we can see what's on the schedule for the next 6 months or so.



#56 Nicole Sharp

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Posted 26 November 2018 - 08:53 PM

Still not sure I understand the exit pupil thing, but on paper, 32 mm looks like it works out really well with 1250 mm of focal length and a Barlow.  A 2X Barlow on a 32-mm eyepiece with a 52-degree AFOV provides a TFOV of 1.2 Lunar diameters, which is the exact same true field of view I would get on a Canon APS-C sensor at prime focus.  So the 32-mm eyepiece basically works as a DSLR simulator, so I can go back and forth between visual observing and prime-focus imaging always seeing the same true field of view (with the 2X Barlow).


Edited by Nicole Sharp, 26 November 2018 - 09:58 PM.


#57 Nicole Sharp

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Posted 26 November 2018 - 09:01 PM

But the field stop is 29 mm on a 27-mm baffle?  Does that mean it would be vignetted?



#58 Nicole Sharp

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Posted 26 November 2018 - 09:56 PM

If I understand the concept of field stop correctly, then I think my best option is to just stick with the 25-mm Plossl that comes with the 5SE.  If I did want to upgrade for a wider apparent field of view, the Celestron X-Cel 25 mm looks like a nice option.  The X-Cel 25 mm would have a TFOV of 2.1 Lunar diameters, and 1.1 Lunar diameters with a 2X Barlow, so that would work out very well too I think.  If the 5SE Plossl has a 52-degree AFOV, then the TFOV is only 1.8 Lunar diameters.


Edited by Nicole Sharp, 26 November 2018 - 10:07 PM.


#59 Nicole Sharp

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Posted 26 November 2018 - 10:24 PM

I just realized this, but I don't think an afocal camera adapter will work with a star diagonal?  I would need a 45-degree erect-image diagonal instead?  A smartphone and camera adapter is over 1 pound in weight.  Can a 5SE focuser with a 45-degree diagonal handle that?



#60 Conaxian

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Posted 26 November 2018 - 11:06 PM

I know nothing of the AP world, and less about the 5SE. That said, any goto mount will be more accurate and less frustrating to use if it is accurately aligned on its first targets. I never saw you mention it, but a reticle eyepiece is an easy way to get that tight goto alignment.  Agena sells a nice one, 20mm, has a removable illuminator with a perfectly smooth switch/brightness control and focusable reticle.  Mine showed up nicely focused. It oozes quality, so I think it will be good enough for me. That, and a small, rechargable powercell you could velcro to the side arm of the mount might be very useful accessories.

Good luck to you and I hope you do well with your new scope!


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#61 Nicole Sharp

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Posted 26 November 2018 - 11:22 PM

Will a 5X Barlow work on a C5 (1250/125) with a Canon APS-C camera (27-mm sensor)?  My top choices for Barlows right now are the Celestron X-Cel 2X/3X apochromatic set or the Altair 2X/3X/5X apochromatic set.  Orion also has a 2X/3X/5X semiapochromatic set.


Edited by Nicole Sharp, 26 November 2018 - 11:28 PM.


#62 Nicole Sharp

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Posted 26 November 2018 - 11:23 PM

I know nothing of the AP world, and less about the 5SE. That said, any goto mount will be more accurate and less frustrating to use if it is accurately aligned on its first targets. I never saw you mention it, but a reticle eyepiece is an easy way to get that tight goto alignment.  Agena sells a nice one, 20mm, has a removable illuminator with a perfectly smooth switch/brightness control and focusable reticle.  Mine showed up nicely focused. It oozes quality, so I think it will be good enough for me. That, and a small, rechargable powercell you could velcro to the side arm of the mount might be very useful accessories.

Good luck to you and I hope you do well with your new scope!

 

Was thinking of a 24-mm illuminated reticle eyepiece, so I could have better eyerelief and then Barlow it.  Would that work with a 5X Barlow?  5X on 24 mm would be over the maximum useful magnification, but if it is just for alignment, does that matter?  5X on 25 mm would be 250X, which should be the limit for useful magnification on a C5 (under perfect skies and perfect darkness).


Edited by Nicole Sharp, 26 November 2018 - 11:26 PM.


#63 Conaxian

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Posted 26 November 2018 - 11:29 PM

Was thinking of a 24-mm illuminated reticle eyepiece, so I could have better eyerelief and then Barlow it.  Would that work with a 5X Barlow?  5X on 24 mm would be over the maximum useful magnification, but if it is just for alignment, does that matter?  5X on 25 mm would be 250X, which should be the limit for useful magnification on a C5 (under perfect skies and perfect darkness).

I have personally never even seen a 5X barlow. A C5 is a long focus optic. A barlow like that would seem to be extreme but what do I know? I use a 2X and that only on my small refractors.



#64 Nicole Sharp

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Posted 26 November 2018 - 11:29 PM

Or can I get two 2X Barlows and stack them for 4X?  It would be double the weight of a 3X or 5X though so maybe not a good idea.



#65 jallbery

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Posted 27 November 2018 - 01:46 AM

Hm.  I checked the manual, and it says that the package should already include an RS-232 cable.  I guess Celestron wants me to update it as soon as possible too.  But that would mean it's not using USB?  I already have an RS-232 to USB adapter, so I should be good then?

 

https://celestron-si...4 languages.pdf

 

It includes a camera shutter cable too.  I really want to get a Canon M50, but the M50 doesn't have a remote-timer/remote-control port, so it can only be remote-controlled over USB from the PC like a webcam would.  :-(

The manual you are referring to has a 2006 copyright data.  It may have been accurate then.

 

When I bought my Evo with the USB hand controller, Celestron hadn't updated the manual; they just provided an update covering the new features of the HC.

 

 

The current 5SE product page says "USB port: Yes, Hand Control input" (see https://www.celestro...rized-telescope )

 

But it's possible you'll get old stock.  You won't know for sure until you get the scope.


Edited by jallbery, 27 November 2018 - 01:48 AM.


#66 jallbery

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Posted 27 November 2018 - 02:23 AM

But the field stop is 29 mm on a 27-mm baffle?  Does that mean it would be vignetted?

I assume this in reference to my earlier statement:

 

Yes, a C5 with F/6.3 R/C will vignette with a crop sensor camera, but it's not like it is dark in the corners.  You may also want to crop the photos square.  Either way, you may still appreciate the extra space from a compositional standpoint.  And visually, for night time astronomy, I was surprised how well the combo works.  Yes there is detectable falloff at the field edges with a max-field  1.25" eyepiece, but there is useful illumination to the edge.   In the day time, I could see how the 5.6mm exit pupil would cause problems for people (your day-time pupil can't accommodate the exit pupil, so it effectively stops down the scope, making the secondary even harder to ignore), but I find the combo usable at night with even my 35mm Ultima.   Different people have different sensitivities to the shadow of the secondary, though.

Vignetting happens even before you get to a field width the size of the rear baffle.   I doubt a C5 fully illuminates even a 10mm image circle.  After that it vary gradually gets a little dimmer.  And once you pass the 27mm point or so, it dims faster,  and eventually faster still.

 

But remember, human beings don't sense brightness linearly.  We are relatively insensitive to this sort of fall off.   Without a reducer, the 35mm Ultima is no issue at all with a C5,     And with a 0.63X reducer, your effective baffle size is reduced by that same 0.63X factor, so 27mm becomes 17mm.   And yet the C5 still provides some illumination all the way to the edge of an eyepiece with a 27mm (or even 29mm) fieldstop.   I'd rather have the extra field with all its flaws (vignetting, coma, field curvature) than not.  

 

With a camera, vignetting is more obvious, but can be adjusted with post processing.   Or you can crop.  And again, if you crop square, you may get rid of most of that vignetting.

 

 

Still not sure I understand the exit pupil thing, but on paper, 32 mm looks like it works out really well with 1250 mm of focal length and a Barlow.  A 2X Barlow on a 32-mm eyepiece with a 52-degree AFOV provides a TFOV of 1.2 Lunar diameters, which is the exact same true field of view I would get on a Canon APS-C sensor at prime focus.  So the 32-mm eyepiece basically works as a DSLR simulator, so I can go back and forth between visual observing and prime-focus imaging always seeing the same true field of view (with the 2X Barlow).

>>which is the exact same true field of view I would get on a Canon APS-C sensor at prime focus.

I'm a Nikon guy, but last time I checked, Canon DSLR sensors were rectangular.  wink.gif

 

At any rate, that's a pretty tight composition, which is why I might be tempted to use the R/C.

 

Visually, I wouldn't use a 16mm plossl with a C5 to look at the full lunar disk-- I'd use something longer.

 

A 32mm eyepiece with a barlow is often not a good idea.  As I've mentioned before, barlows work better with shorter focal length eyepieces.  



#67 jallbery

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Posted 27 November 2018 - 02:30 AM

Was thinking of a 24-mm illuminated reticle eyepiece, so I could have better eyerelief and then Barlow it.  Would that work with a 5X Barlow?  5X on 24 mm would be over the maximum useful magnification, but if it is just for alignment, does that matter?  5X on 25 mm would be 250X, which should be the limit for useful magnification on a C5 (under perfect skies and perfect darkness).

Why do you care about eye relief for a reticle eyepiece?   This baffles me.  You seem to think some sort of ultra-precise alignment is going to solve all sorts of ills, and I doubt it will. 

 

And yes you can stack barlows, but again, why?

 

Defocus the star to help you tell what centered is.


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#68 Nicole Sharp

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Posted 27 November 2018 - 02:34 AM

Why do you care about eye relief for a reticle eyepiece?   This baffles me.  You seem to think some sort of ultra-precise alignment is going to solve all sorts of ills, and I doubt it will. 

 

And yes you can stack barlows, but again, why?

 

Defocus the star to help you tell what centered is.

Going with the 24-mm reticle since it has the most eyerelief.  There is a 20-mm reticle with a wider AFOV and a wider TFOV, but it has less eyerelief.  I wear eyeglasses, so I need all the eyerelief I can get.  The 24-mm reticle has 20 mm of eyerelief and the 20-mm reticle has 16 mm of eyerelief.  But the 20-mm also costs four times as much in addition to having less eyerelief, so not worth it for a wider field of view.


Edited by Nicole Sharp, 27 November 2018 - 02:36 AM.


#69 jallbery

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Posted 27 November 2018 - 02:37 AM

I just realized this, but I don't think an afocal camera adapter will work with a star diagonal?  I would need a 45-degree erect-image diagonal instead?  A smartphone and camera adapter is over 1 pound in weight.  Can a 5SE focuser with a 45-degree diagonal handle that?

>>I just realized this, but I don't think an afocal camera adapter will work with a star diagonal?

Why not?

 

If you are worried about the image being backwards, just flip it.



#70 Nicole Sharp

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Posted 27 November 2018 - 02:38 AM

Still trying to figure out if a 5X Barlow would work with a Canon APS-C camera on the C5.  I am guessing maybe but only under absolutely perfect weather from an extremely dark-sky site.  Getting the 2X/3X apochromatic set would be cheaper too.



#71 Nicole Sharp

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Posted 27 November 2018 - 02:39 AM

>>I just realized this, but I don't think an afocal camera adapter will work with a star diagonal?

Why not?

 

If you are worried about the image being backwards, just flip it.

It's too wide?  I'll find out when the telescope arrives, but my guess is that it will not fit in the space between the tube and the camera mount.  I sent an email to Celestron about the weight capacity on the focuser and diagonal.  Will a DSLR camera work with an erect-image diagonal?  That would put 2.8 pounds of weight on the focuser.



#72 jallbery

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Posted 27 November 2018 - 02:45 AM

Going with the 24-mm reticle since it has the most eyerelief.  There is a 20-mm reticle with a wider AFOV and a wider TFOV, but it has less eyerelief.  I wear eyeglasses, so I need all the eyerelief I can get.  The 24-mm reticle has 20 mm of eyerelief and the 20-mm reticle has 16 mm of eyerelief.  But the 20-mm also costs four times as much in addition to having less eyerelief, so not worth it for a wider field of view.

I wear glasses too, but I'd find taking off my glasses to use a 12mm reticle eyepiece less hassle than stacking barlows.



#73 Nicole Sharp

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Posted 27 November 2018 - 02:56 AM

I wear glasses too, but I'd find taking off my glasses to use a 12mm reticle eyepiece less hassle than stacking barlows.

A 24-mm reticle and a 3X Barlow works as an 8-mm reticle, but with four times the eyerelief as a 9-mm reticle.



#74 jallbery

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Posted 27 November 2018 - 02:59 AM

And as my final bit of advise...  just get the SCT prime focus adapter if you want to use a DSLR camera.  It's solid and doesn't flex.

 

Still trying to figure out if a 5X Barlow would work with a Canon APS-C camera on the C5.  I am guessing maybe but only under absolutely perfect weather from an extremely dark-sky site.  Getting the 2X/3X apochromatic set would be cheaper too.

Why would you WANT to use a 5X barlow with a crop sensor camera on a C5?

 

A C5 has about a 1 second of resolution.

 

The 22mm wide sensor gives you a degree-wide field.  Divide that by 6000 (roughly the number of horizontal pixels for a 24MP camera) and your pixels are already smaller than the smallest detail the scope show.  


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#75 Nicole Sharp

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Posted 27 November 2018 - 04:06 AM

And as my final bit of advise...  just get the SCT prime focus adapter if you want to use a DSLR camera.  It's solid and doesn't flex.

 

Why would you WANT to use a 5X barlow with a crop sensor camera on a C5?

 

A C5 has about a 1 second of resolution.

 

The 22mm wide sensor gives you a degree-wide field.  Divide that by 6000 (roughly the number of horizontal pixels for a 24MP camera) and your pixels are already smaller than the smallest detail the scope show.  

Yes, Celestron recommended the SCT T-adapter over the universal adapter as well, but was ambiguous as to the technical reasons why.  I think it might just weigh less perhaps.

 

I heard back from Canon and the M6 is the only M-series camera that will support a handheld intervalometer, and the M50 is the only M-series camera that will support a PC intervalometer.  So if I want to be able to do both, I have to get an SL2 instead.  Still trying to avoid the Sony star eaters.  The whole point of getting a handheld camera in the first place is so I don't need to buy an expensive new laptop, or run a laptop out in the field at all, for unguided imaging.

 

Gonna go with the Celestron X-Cel 2X/3X apochromatic Barlows.  If I ever wanted 5X, then I can add an Altair.  All the Barlows don't really have to be in a matched set, and the X-Cel weighs less and costs less than the Altair does.

 

Keep the 25-mm kit Plossl as my primary visual observing eyepiece, and then add a 24-mm reticle for alignment.  The 25-mm X-Cel eyepiece actually has less eyerelief than an Orion 25-mm Plossl.  Not sure what the eyerelief or AFOV on the 5SE kit eyepiece is though.

 

I also found a good deal on a Meade Adventure Scope 60 (360/60) to use as a wide-field 'scope.  I know it's not as good as a 400/80 would be, but I still want to minimize the chromatic aberration (plus it weighs less, if I want to use it for autoguiding or long exposures).  It comes with a 1.25" erect-image diagonal that I should be able to use on the SCT as well for terrestrial observing.  I should be able to mount it to the 5SE fork with a tripod-to-Vixen adapter.


Edited by Nicole Sharp, 27 November 2018 - 04:10 AM.

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