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First light with a cheap 130/650 f/5

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#1 Tannhäuser Gate

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Posted 30 December 2019 - 09:20 PM

I just received a Gskyer 130 EQ mounted scope from ebay. It was $135 open box so I thought I would take a chance. This will be my 3rd scope after getting back into the hobby after my Celestron C90 and Meade adventure scope (ST80) that I bought this summer. It looks to me just like a synta made skywatcher clone.

 

The mount is pretty banged up but it's also what I would call Chineseum and I didn't buy this for that. However after I replace a couple of bent knobs I do plan on getting in some equatorial practice with it. The tripod is ok. Probably slightly more substantial than my AZ-GTi. I'll most likely be passing on the mount and tripod. I just really wanted the scope.

 

3jtKKc7h.jpg

 

Before I found this I considered the Zhumell z130 as it looked like a nice scope but I didn't really want a table top mount and this was about $65 cheaper and the Z130 needs to be upgraded a little for quicker collimation. This has rings and a dovetail and a decent 1.25 focuser. The finderscope is nothing special and neither are the eyepieces. Fortunately at F5 I'm not really worried about the finderscope and I have another RACI scope I can use if I want. I have a nice assortment of eyepieces already as well.

 

With some trepidation I put it on my AZ GTi mount and it's worked without protesting tonight in AZ mode. Gotos and tracking the moon earlier seemed fine. The scope comes in at around I think 9 pounds so it's under the 11 pound limit of the mount. Having said that I would say this is the limit of the mount and I wish I had a heavier and more substantial tripod to put it on. I'm looking at a berlebach model in the future and probably another robust manual AZ mount.

 

I'm going to go back out in a little while when orion is higher and check the collimation at higher power. Next step is to make or buy a collimator cap. I might go crazy when my new ZWO camera gets here and try the scope in EQ mode on the AZ GTi. Not expecting great results, but you never know.

So far I'm liking my first newt!


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#2 vtornado

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Posted 30 December 2019 - 10:15 PM

It's a beaut!  Looks Pretty, and nicer focuser than I have seen on some of the other 130's.



#3 Tannhäuser Gate

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Posted 31 December 2019 - 01:10 AM

Got back out for an hour or so and tried out my higher powered plossls. Seeing was not great and I'm under white zone skies with limited sky to point at from my driveway but I make it work. I can tell the scope is a bump up from my ST80 with the higher powered eyepieces. To my newb eyes collimation appears good. Stars weren't exactly pinpricks at high power but they're round and turn into nice round donuts in and out of focus.

 

Took a look at a dimming beetleguese, Uranus with I think a hint at its moons. The Pleiades looked great back down with the 32 plossl.

 

M42 looked better than I'd ever seen it at all powers. And it looks spectacular to my eyes with my $13 UHC filter.

 

It's definitely a different experience looking through the eyepiece on this reflector as opposed to my mak and my refractor. Just a bit higher at most views than is perfect viewing on my camp stool, but being able to rotate the tube in the rings brings it to an accessable height.

 

(If this post would have been more appropriate in the beginner forum I apologize.)

 

hyugf8Ah.jpg


Edited by Tannhäuser Gate, 31 December 2019 - 07:53 PM.


#4 Jon Isaacs

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Posted 31 December 2019 - 09:28 AM

I like 130 mm F/5 Newtonians. If the optics are decent, they're the closest thing to a budget 4 inch apo you can buy.

 

The focuser appears to be a Crayford, that's a good thing. It looks like a 2 inch Orion focuser,, there's no adapter?

 

Have fun..

 

Jon


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#5 Don H

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Posted 31 December 2019 - 02:40 PM

Congratulations, it looks like you found a nice scope. If you were to rotate your mount 180 degrees, then remove your OTA and place it back in the rings with the mirror side at the other end (and the open end back pointing at the sky), your focuser wheels will be below the eyepiece and your finder shoe will be at the top of the tube. Just a suggestion. If you are more comfortable with the setup as is, enjoy and Happy New Year!



#6 Tannhäuser Gate

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Posted 31 December 2019 - 03:49 PM

I'm running the AZ-GTi with a firmware update which enabled equatorial mode and right-arm az. For some reason updating the firmware to add the eq mode also inverts the az function. So that's why the focuser is upside down, which is a bit weird.

#7 Don H

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Posted 31 December 2019 - 04:58 PM

If you don't want it upside down, another option is to just undo the 4 focuser screws and rotate just the focuser 180 degrees. Then you could drill 2 new holes for the finder on the other side. Just do all your work with the primary end higher than the secondary, so any dropped hardware falls away from your mirrors to the floor. Might be better to leave it as is and enjoy it for a while. Tinkering can always be done during a long stretch of cloudy nights...



#8 SteveG

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Posted 31 December 2019 - 07:48 PM

I'm also into these 5" f5 reflectors. Did this come with a focus tube extender? Does the focuser have enough range to focus all of your eyepieces without an extension tube?



#9 clearwaterdave

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Posted 01 January 2020 - 03:00 AM

That's a sharp looking scope.,I love my 130.,it's my most used scope because it puts up great views and is easy to carry out and be viewing.,cheers.,

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#10 Tannhäuser Gate

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Posted 01 January 2020 - 02:18 PM

I like 130 mm F/5 Newtonians. If the optics are decent, they're the closest thing to a budget 4 inch apo you can buy.

 

The focuser appears to be a Crayford, that's a good thing. It looks like a 2 inch Orion focuser,, there's no adapter?

 

Have fun..

 

Jon

 

One of my upcoming goals is to suss out all the different types of refractors. I'll read about a refractor type online and I can look it up but I don't yet have a sort of mental heirarchy of where they all fit. I know my inexpensive ST80 is at the very low end (yet not crap end) and I know that refractors seem to get very expensive quickly. I digressed a little.

 

I upgraded aforementioned ST80 to a lunt/gso dual speed crayford and the focuser on this 130 reflector feels like the action on that and it has the 2 locking screws on the bottom (or top in the current orientation). It's kind of squeaky so I may open it up a little and take a look to see if there's anything I can do to smooth it out. I haven't looked the subject up yet. Are their any good crayford focuser maintenance articles out there?

 

It's not a 2" unfortunately. Maybe it can be replaced easily? I could upload a close up of the assembly on the scope.

 

 

If you don't want it upside down, another option is to just undo the 4 focuser screws and rotate just the focuser 180 degrees. Then you could drill 2 new holes for the finder on the other side. Just do all your work with the primary end higher than the secondary, so any dropped hardware falls away from your mirrors to the floor. Might be better to leave it as is and enjoy it for a while. Tinkering can always be done during a long stretch of cloudy nights...

 

Aside from the focuser being upside down currently on this mount the orientation doesn't bug me at all.

 

This sort of leads into another subject as I'm left handed. I'm also left footed and left eyed. Shoot left handed, left eye dominate etc. I haven't even looked up how left handedness is taken into account (if ever) in astronomy.

 

I'll take your scope surgery advice into account but I'll probably hold off on this OTA as I bought it mostly for a future mount on which it won't need to be saddled "backwards".


Edited by Tannhäuser Gate, 01 January 2020 - 03:12 PM.


#11 Tannhäuser Gate

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Posted 01 January 2020 - 02:32 PM

I'm also into these 5" f5 reflectors. Did this come with a focus tube extender? Does the focuser have enough range to focus all of your eyepieces without an extension tube?

It didn't come with an extender. I have to draw the focuser out a lot but it has attained focus with the 3 plossl eyepieces and the 2x barlow I've used so far.


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#12 Volvonium

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Posted 03 January 2020 - 04:17 AM

How far can you push it magnification wise?  I always assumed the Gskyer used a spherical primary mirror, rather than parabolic, as Gskyer is a notorious "Alley Express" Chinesium brand.   I've got a 130mm f/5 with Zhumell 130 optics and it's a really nice performer.  If you can push that Gskyer past 100-120X and still get a focused image, there's a chance it has a parabolic mirror.   I could never get a spherical 130mm to go past 120X, even with perfect collimation.  With a parabolic, it was almost effortless to hit up to 200X on good nights.

 

Is that focuser all metal?     

 

It's a lot of fun to push the limits of these small newts!


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#13 Pinbout

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Posted 03 January 2020 - 10:56 AM

use an 5mm eyepiece to do a star test, no barlows.

 

and two pennies to do a star test, one penny for focused, no pennies for inside, two pennies for outside focus...

 

my primary wasn't very good. I have since stripped it and corrected it.

 

before I corrected it.

med_gallery_106859_355_96928.jpg


Edited by Pinbout, 03 January 2020 - 10:57 AM.


#14 Tannhäuser Gate

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Posted 03 January 2020 - 07:56 PM

How far can you push it magnification wise?  I always assumed the Gskyer used a spherical primary mirror, rather than parabolic, as Gskyer is a notorious "Alley Express" Chinesium brand.   I've got a 130mm f/5 with Zhumell 130 optics and it's a really nice performer.  If you can push that Gskyer past 100-120X and still get a focused image, there's a chance it has a parabolic mirror.   I could never get a spherical 130mm to go past 120X, even with perfect collimation.  With a parabolic, it was almost effortless to hit up to 200X on good nights.

 

Is that focuser all metal?     

 

It's a lot of fun to push the limits of these small newts!

The last night it was clear I was able to see uranus (albeit small and faintly) with my 9mm plossl and 2x barlow. So 144x? The seeing was not great and I'm sure the scope needs to be collimated properly. I plan on doing that soon.

 

You have me concerned, but not greatly as at least my cash outlay was not great and I consider all of this education right now. I got home tonight and took it out onto the driveway to try and catch venus before it dropped below a roof line and it looked pretty bright and misshapen and dreadful in 9mm. Having said that I didn't let the scope cool down really at all. To compare I took my C90 out quickly as well (again, not a proper cooldown) and venus actually looked pretty bad in it as well, so I'm not sure. Jupiter, Saturn and even Uranus looked outstanding this summer in the C90.

 

So plan now is, proper collimation, proper cooldown and test it out on bright objects with some good seeing. Lots to learn!

 

And yes, the focuser is all metal.

 

use an 5mm eyepiece to do a star test, no barlows.

 

and two pennies to do a star test, one penny for focused, no pennies for inside, two pennies for outside focus...

 

my primary wasn't very good. I have since stripped it and corrected it.

 

before I corrected it.

med_gallery_106859_355_96928.jpg

Could you explain the penny test in more detail? I'm familiar with a star test but the penny part I can't find any information on.


Edited by Tannhäuser Gate, 03 January 2020 - 07:58 PM.


#15 Pinbout

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Posted 03 January 2020 - 08:07 PM

You want to measure same distance from best focus for inside focus and outside focus

 

so you use shins, pennies just seems like a common Item that comes close to an appropriate dimension

 

put 1 penny under the eyepiece shoulder then find best focus

 

remove the penny and let the eyepiece slide down so inside focus is the distance of the penny’s thickness

then put 2 pennies under the eyepiece shoulder so the outside focus is 1penny thickness further away from best focus

 

use your cell to take pics of both inside/outside focus

 

my pic above is about 1/2 -1 wavefront overcorrected.

 

the side that has a larger CO has the weighted correction:

 

inside bigger - under

outside bigger - over 

 

of course I’m simplifying it but to know overall correction - this is what you do.


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#16 Pinbout

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Posted 03 January 2020 - 08:12 PM

Your an f5 scope

 

a 5mm eyepiece gives a 1mm exit pupil - a 1mm exit pupil presents the best overal image from the optics.

 

so a 9mm with a 2x’s Barlow makes you below .5mm exit pupil - you shouldn’t go below .5mm and expect the same quality views 

 

Barlow’s also add correction so if your below .5mm with a Barlow that could make things even softer...

 

just saying 


Edited by Pinbout, 03 January 2020 - 08:13 PM.


#17 Tannhäuser Gate

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Posted 03 January 2020 - 08:30 PM

You want to measure same distance from best focus for inside focus and outside focus

 

so you use shins, pennies just seems like a common Item that comes close to an appropriate dimension

 

put 1 penny under the eyepiece shoulder then find best focus

 

remove the penny and let the eyepiece slide down so inside focus is the distance of the penny’s thickness

then put 2 pennies under the eyepiece shoulder so the outside focus is 1penny thickness further away from best focus

 

use your cell to take pics of both inside/outside focus

 

my pic above is about 1/2 -1 wavefront overcorrected.

 

the side that has a larger CO has the weighted correction:

 

inside bigger - under

outside bigger - over 

 

of course I’m simplifying it but to know overall correction - this is what you do.

Oh my gosh. Use the pennies as shims under the eyepiece rim! Ok I get it now. I'll have to try this out soon. Here I was thinking you wanted me to aim at a penny off in a field or something.



#18 Jon Isaacs

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Posted 04 January 2020 - 08:16 AM

Your an f5 scope

 

a 5mm eyepiece gives a 1mm exit pupil - a 1mm exit pupil presents the best overal image from the optics.

 

so a 9mm with a 2x’s Barlow makes you below .5mm exit pupil - you shouldn’t go below .5mm and expect the same quality views

 

I like the penny technique... 

 

A 9mm with a 2x Barlow = 4.5mm and at F/5 provides a 0.9mm exit pupil.  I have had many wonderful views with 0.9 mm exit pupils and below.

 

The exit pupil is about the matching the image to the eye, it doesn't change the image at the focal plane.  

 

Just saying.

 

Jon



#19 Tannhäuser Gate

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Posted 04 January 2020 - 08:23 PM

Marked center on the primary to the best of my ability. Cooling the scope down right now. I'm going to have a look at high power and then bring it in and make a collimator cap and see if I can get it dialed in.

 

CIsd6uth.jpg


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#20 Pinbout

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Posted 04 January 2020 - 11:36 PM

I like the penny technique... 

 

A 9mm with a 2x Barlow = 4.5mm and at F/5 provides a 0.9mm exit pupil.  I have had many wonderful views with 0.9 mm exit pupils and below.

 

The exit pupil is about the matching the image to the eye, it doesn't change the image at the focal plane.  

 

Just saying.

 

Jon

Yeah my math is wrong tongue2.gif


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