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Help With a few Problems with my Celestron Nexstar SLT [BEGINNER]

accessories beginner Celestron collimation equipment eyepieces reflector
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#1 charliekempf

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Posted 15 July 2019 - 07:14 PM

Hi everyone,

 

A bit of backstory:

Recently, the basement in my house in Chicago was flooded, and my mom and I flew out to assess the damage and attempt to fix it (we hadn't lived there in a while). Long story short, I was cleaning out the basement when I discovered a Celestron Nexstar SLT 114, a telescope gifted to me when I was far too young to operate it. I've spent the past few days attempting to restore it to working condition.

My basement was submerged a few inches deep in water, so thankfully the telescope tube, although a bit dusty, was completely unharmed, along with the motorized mount. However, that's really my only saving grace. Below are a few of the complications I've had so far:

LENSES:

Alongside my telescope, I also received one of those fancy celestron lens kits. This has been since lost to time (believe me I looked), as such, the only lens I currently have with my telescope is a 4mm one, along with a 23mm one I recently purchased off of Amazon. The 4mm I found in the focusing tube when I dug it out of the basement, which isn't surprising as younger me fell for the classic blunder "more magnification = better." I've considered buying more lenses but I wanted to make this post first because I'm trying not to spend to much money.

 

REMOTE:

The bottom of the remote was submerged in water. The LCD was impossible with only a few select pixels working, however the arrow keys were still working, so I assumed it was fully functional. I know it was the remote because I've tried it on the AUX and HAND CONTROL ports of my telescope with the exact same result. I attempted to clean the PCB of the remote in order to potentially restore the rest of the LCD, and ended up breaking it entirely. I have already ordered a replacement off of eBay, but that wont be here for a week, so I would like to get some kind of jank setup working in order to use the dang thing.

COLLIMATION:

I suspected my younger self screwed around with the alignment without knowing what the knobs on the back actually were, and sure enough, upon a quick test run pointed at the moon, my picture was very fuzzy. I know there are many different guides out there, but most videos and posts I read work with Primary mirrors with the little Collimation doughnuts in the middle, which mine doesn't have. Due to me losing all the accessories for the telescope, I have no tools in order to Collimate, not even a cap. I've read that laser collimation can be janky, that the cheshire ones require the doughnut thing, and I also read online that my telescope has a 2x barlow built into the focusing tube, and I'm really not in the mood to screw around with that if I have other alternatives. Also, since I don't have a working remote, I can only tilt my telescope up and down, not side to side (I have to physically re-position the telescope) which is very clunky and makes it impossible to reliably aim at something. So what are my options in terms of collimation (I'm open to taking it to a store and having them do it if that sort of thing exists) and how do I carry out those options?

 

TL;DR

 

- I cannot move my telescope due to a broken remote

- I only have 23mm and 4mm lenses, no other eyepieces of any kind

- How do I collimate it with no materials, and no collimation doughnut on my primary mirror?

- What other accessories do I NEED to buy in order to have a good time? (I've already ordered a new remote, ETA 1 Week)

- Is there a cheap way to connect the PC to the telescope without a working remote? (Sub $50)

- What software on PC should I get to maintain and use the telescope? (I currently have the Celestron Firmware Manager, NexRemote and Stellarium)

- What are some methods to use my telescope until my new remote arrives

- I ordered the exact same remote I originally had, but are the new ones with USBs compatible with my telescope?

Thanks,

Charlie



#2 Michael_Swanson

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Posted 15 July 2019 - 08:07 PM

Hi Charlie,

 

First off, on this page of my website, have a read through the "Accessories for Your Scope" article:

https://www.nexstars...OddsEndsSLT.htm

It discusses items you are interested in (including eyepieces) and some you haven't thought of.

 

Regarding collimation, at a minimum you will need a collimation peep sight.  The last time I owned a Newtonian reflector, I made one from a 35mm film canister.  If you Google "Newtonian reflector collimation" you should find good instructions.

 

There is no < $50 off-the-shelf accessory to connect a PC to the scope.  Basically you need either a hand control (HC) like the one you ordered, a Celestron SkyPortal WiFi module ($100), the discontinued Celestron AUX Port Adapter, a homemade version of the WiFi module (a few Raspberry Pi projects have been presented here on Cloudy Nights) or a homemade version of the AUX Port Adapter (for an example, back on that page I linked to above, see Ken Hutchinson's article).  I expect you will have the hand control (HC) you ordered before you could attempt any other option and that will be all you really need.  There isn't really a way to use the scope until you get the HC or one of these other options.

 

Regarding connection of external computers (PC/smartphone/tablet), have a careful read through this section of my website:

https://www.nexstars...m/PCControl.htm

 

CPWI is the new replacement for NexRemote - either will work with your scope:

https://www.nexstars...ontrol/CPWI.htm

 

Yes, the latest NexStar+ HCs with USB port are compatible with your scope:

https://www.nexstars...NexStarPlus.htm

 

Best regards,
Mike Swanson
Author of "The NexStar Users Guide II"
Author of "The NexStar Users Guide"
Author of "NexStar Observer List"
https://www.nexstarsite.com



#3 charliekempf

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Posted 15 July 2019 - 08:15 PM

Hi Charlie,

 

First off, on this page of my website, have a read through the "Accessories for Your Scope" article:

https://www.nexstars...OddsEndsSLT.htm

It discusses items you are interested in (including eyepieces) and some you haven't thought of.

 

Regarding collimation, at a minimum you will need a collimation peep sight.  The last time I owned a Newtonian reflector, I made one from a 35mm film canister.  If you Google "Newtonian reflector collimation" you should find good instructions.

 

There is no < $50 off-the-shelf accessory to connect a PC to the scope.  Basically you need either a hand control (HC) like the one you ordered, a Celestron SkyPortal WiFi module ($100), the discontinued Celestron AUX Port Adapter, a homemade version of the WiFi module (a few Raspberry Pi projects have been presented here on Cloudy Nights) or a homemade version of the AUX Port Adapter (for an example, back on that page I linked to above, see Ken Hutchinson's article).  I expect you will have the hand control (HC) you ordered before you could attempt any other option and that will be all you really need.  There isn't really a way to use the scope until you get the HC or one of these other options.

 

Regarding connection of external computers (PC/smartphone/tablet), have a careful read through this section of my website:

https://www.nexstars...m/PCControl.htm

 

CPWI is the new replacement for NexRemote - either will work with your scope:

https://www.nexstars...ontrol/CPWI.htm

 

Yes, the latest NexStar+ HCs with USB port are compatible with your scope:

https://www.nexstars...NexStarPlus.htm

 

Best regards,
Mike Swanson
Author of "The NexStar Users Guide II"
Author of "The NexStar Users Guide"
Author of "NexStar Observer List"
https://www.nexstarsite.com

Awesome! Thank you so much!



#4 oldstargazer

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Posted 15 July 2019 - 09:00 PM

https://s3.amazonaws...7_nexstargt.pdf

 

link to owners manual for your scope



#5 oldstargazer

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Posted 15 July 2019 - 09:12 PM

a defocused star collimation.PNG

 

a way to do collimation by creating rings around a star and then making sure they are the same all around



#6 Michael_Swanson

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Posted 15 July 2019 - 10:23 PM

https://s3.amazonaws...7_nexstargt.pdf

 

link to owners manual for your scope

That's probably the wrong manual unless Charlie is mistaken about which scope he owns which I realize after re-reading, is definitely possible.

 

Charlie - is the optical tube of your scope mounted to the arm via a short rail (dovetail bar) or a large circular clamp?  If circular clamp, your scope is not a NexStar SLT but rather a NexStar 114 GT.  If NexStar 114 GT, the only commonly available hand control compatible with that mount is the version 4 hand control.  The NexStar+ HC is NOT generally compatible with that mount (though there are exceptions if the scope was manufactured within the last 5-6 years).  When using the version 4 hand control with the older NexStar GT mounts, you must use HCupdate to load the GT 4.03 firmware:

https://www.nexstars...wToVersion4.htm

 

And, CPWI is not compatible with the NexStar GT, nor is the SkyPortal WiFi module.

 

This is the section of my website for the NexStar GT series:

https://www.nexstars.../OddsEndsGT.htm

 

Best regards,
Mike Swanson
Author of "The NexStar Users Guide II"
Author of "The NexStar Users Guide"
Author of "NexStar Observer List"
https://www.nexstarsite.com



#7 charliekempf

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Posted 15 July 2019 - 11:23 PM

That's probably the wrong manual unless Charlie is mistaken about which scope he owns which I realize after re-reading, is definitely possible.

 

Charlie - is the optical tube of your scope mounted to the arm via a short rail (dovetail bar) or a large circular clamp?  If circular clamp, your scope is not a NexStar SLT but rather a NexStar 114 GT.  If NexStar 114 GT, the only commonly available hand control compatible with that mount is the version 4 hand control.  The NexStar+ HC is NOT generally compatible with that mount (though there are exceptions if the scope was manufactured within the last 5-6 years).  When using the version 4 hand control with the older NexStar GT mounts, you must use HCupdate to load the GT 4.03 firmware:

https://www.nexstars...wToVersion4.htm

 

And, CPWI is not compatible with the NexStar GT, nor is the SkyPortal WiFi module.

 

This is the section of my website for the NexStar GT series:

https://www.nexstars.../OddsEndsGT.htm

 

Best regards,
Mike Swanson
Author of "The NexStar Users Guide II"
Author of "The NexStar Users Guide"
Author of "NexStar Observer List"
https://www.nexstarsite.com

It's the SLT, it's mounted via the dovetail, and also it says "Nexstar 114 SLT" on the telescope tube.



#8 Michael_Swanson

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Posted 15 July 2019 - 11:35 PM

In that case, if you are missing the manual, see the SLT section of this page of my website:

https://www.nexstars...com/Manuals.htm

 

And everything I said in my first reply applies.

 

Oh, and another point - pretty much any small optical tube can be used on that mount.



#9 charliekempf

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Posted 15 July 2019 - 11:38 PM

In that case, if you are missing the manual, see the SLT section of this page of my website:

https://www.nexstars...com/Manuals.htm

 

And everything I said in my first reply applies.

 

Oh, and another point - pretty much any small optical tube can be used on that mount.

One more thing, If I were to purchase a tool for collimation, what are my options (given that the 114 slt doesn't have a centering dot)?



#10 Michael_Swanson

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Posted 15 July 2019 - 11:58 PM

There are guides on the Internet describing how to remove the rear cell and apply your own center dot.  I also describe it in my book.  However, as I also note in my book, the adjustment capabilities on the 114mm Celestron Newt are rudimentary and really, about the best you can do is adjust the rear cell (those 6 screws on the bottom/back of the scope).  First off, you need a night of steady seeing conditions and the scope must be cooled to the outside temperature.

 

There is a bit of detail to the process but basically, find a bright star (around 2nd magnitude is best) and very accurately center it in a moderate magnification eyepiece.  Polaris is a good choice as it isn't moving (much).  Defocus slightly until you see concentric circles with a dark shadow in the center (Ralph's image above).  If the rings are not concentric, loosen the three cross-tip screws (they are locking screws) on the back of the primary mirror cell (the bottom/back of the scope) by about 1/2 turn.  Then, while observing the rings in the eyepiece, very slightly turn one of the thumbscrews on the primary mirror cell. This will either improve or worsen the concentricity of the rings. With careful adjustments to just two of the thumbscrews, you should be able to center the rings. If a thumbscrew will move no more, loosen the corresponding cross-tip screw slightly.  Each time you make an adjustment it is important to precisely re-center the defocused image in the field of view.  Repeat until you have concentric circles.  You can then increase the magnification if the image is steady and repeat for a more precise collimation.

 

After you are satisfied with the results, tighten the three cross-tip screws to lock the primary mirror in place. Note that this might somewhat alter collimation, so it would be necessary to slightly adjust the thumbscrews again.

 

Final note - most of the Newtonian collimation aids you can purchase will not work with your 114 - that built-in focal adjuster/flattener gets in the way.  And removing it, even temporarily, doesn't work.  Hopefully your secondary mirror (the diagonal mirror up at the front) is still well-adjusted as that is the hard adjustment that the aids really work with.

 

Best regards,
Mike Swanson
Author of "The NexStar Users Guide II"
Author of "The NexStar Users Guide"
Author of "NexStar Observer List"
https://www.nexstarsite.com




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