Build a Equatorial Wedge for 130 slt
Posted 04 December 2009 - 02:23 PM
Posted 04 December 2009 - 03:28 PM
A very warm welcome to CN and to this our Nexstar forum.
I've never built a wedge, but have used the Celestron unit in combination with my Nexstar 8i although admittedly with not much success.
Would this website perhaps help? (bottom of the page describes amateur wedge construction).
Posted 05 December 2009 - 12:46 PM
I would like to do the same.
Let me know, please if you have some more ideas.
Posted 06 December 2009 - 04:45 AM
One important question has just occurred to me this morning, the answer to which may well "scupper" this idea at the onset.
Is the SLT series capable, at all, of being EQ aligned ?
The manual would suggest not, in which case, while these 'scopes may physically be mounted on a wedge, purchased or homemade, no "GoTo" will be possible.
What do you think ?
Posted 13 December 2009 - 12:44 PM
First you have to know that I am very newbee in using a scope. I've purchased my first one (130 SLT)last september and I've not made any photos yet.
I read on the manual that the scope can be EQ North or South align by using a wedge and it have also a sideral tracking.
Of course, I know that the Azimutal mount is not the best for doing Astrophotography having read a lot of posts on the net (I should I've known better), but I also read that for doing so, you need a lot of expensive materials and that is too much for me.
I'm just wondering to me, having purchased this scope, what is the best I can do with it?
Please don't take care of my bad speeking english.
Posted 13 December 2009 - 01:49 PM
A very warm welcome to CN and, as a Nexstar owner, a special welcome to this forum. Please make no apology for your English. We, or should I say you, have absolutely no problem with it !
I cannot see however, where, in the 130SLT manual, you saw that you can carry out an EQ North, (or South) Align. (?) I have looked through the (attached) manual and only see:
Auto Two Star Align.
Two Star Align.
One Star Align.
Solar System Align.
With tracking, the mount has four possible settings:
If I am correct and there IS no way you can align your 130SLT equatorially, you will still be able to carry out quite reasonable astrophotography and not too expensively.
Starting out, try only lunar and planetary imaging. With care, you will get good results.
Ideally, all you need is a fast frame camera like the Celestron Neximage or a suitable webcam, (with an adapter so that it fits your focusing tube).
If you need further advice on this please just ask. We're all here to help each other.
Posted 13 December 2009 - 06:07 PM
Thank you for your answer.
As I am not so good yet with all these technics and terms in using a scope I certainly make a mistake.
I read at the end of page 20 of the manual, in the paragraph "Set up Procedures" what I said before.
I was thinking that doing this and with a good polar alignment, I will be able to make an "equatorially like" scope, even if I have to built a motor driven wedge.
I have to learn more about all of this. I will begin, as you said, by making lunar and planetary imaging with a webcam first, I will go on perhaps on deep sky later with appropriate scope and ccd camera if I can.
Thank you and best regards,
Posted 13 December 2009 - 07:10 PM
No problem: we all had to start somewhere !
Yes, I see what you mean about page 20 which refers under "Set Up Procedures" to "Tracking Modes" within the hand controller. It does not refer to alignments.
If though, you take a look at the " Nexstar Menu Tree" scheme on page 25, you will see that while EQ North and EQ South is shown under "Menu" ----> "Tracking" ----> "Mode": there is no "EQ (North or South) Alignment" in the Alignment column immediately right of the "Menu" column.
For this reason, your 130 SLT cannot be EQ aligned.
These hand controllers do serve other Nexstar telescopes which can "EQ Align".
Using a webcam will bring you good imaging results but practice will be needed if you have never done this before.
There are plenty of people here to help you if you need it.
Just please ask !
Posted 19 December 2009 - 11:29 PM
I was specifically doing it for tracking with a Nikon camera; I also tried with a C6 OTA, but the weight was too much due to the SLT being an unbalanced mount.
If you want to use with a lighter OTA then you'll still have some issues with the tube not being able to reach below about 30 degrees south - due to the curved fork it means the wedge gets in the way.
I've posted some photos here:
Posted 19 December 2009 - 11:46 PM
Instead of a wooden wedge, you should also check out the last two photos at the bottom of this page - Daniel Ciobota was originally using the 'wedge-pod' (Celestron 93497) with an SLT adapted to fit on top and got some good results.
Posted 20 December 2009 - 05:52 AM
Thanks for pitching in on this. From what I'd seen, EQ alignment was a non-starter ! I'm sure Dave and Blackhole will be well pleased with this information and the rest of us, all the wiser !
Posted 20 December 2009 - 08:15 AM
Posted 20 December 2009 - 09:13 AM
Auto two star
This is using firmware version 4.13 on the hand controller.
After selecting EQ north align there is another menu with EQ choices as follows:
EQ Two star
EQ One star
EQ Solar system
As a test, I mounted the SLT on my wooden wedge and polar aligned roughly.
Then I chose EQ one star, and used Rigel for the fine alignment.
The photos at the link I sent above were quick 30sec test exposures on the Nikon, with tracking active after the EQ align. No star trails were visible.
Posted 20 December 2009 - 09:39 PM
If you have a finderscope you can 'eyeball' this on Polaris for EQ North, but in my case I was using a camera so it was a bit more tricky.
Because the SLT doesn't have any 'home' location marks on either of the mount axis, the easiest quick way I could find is to start with the azimuth motor (left/right buttons) rotated so that the curve of the fork is pointing upwards, then I used a spirit level help against the OTA, and pressed up/down buttons on the hand controller to move the altitude motor until the OTA was horizontal.
Now, power off and on to reset the axis encoder counters, and using the axis position display in the hand controller raise the OTA upwards on the altitude motor for the same number of degrees as your latitude (i.e. the wedge angle)
Move the tripod left or right to get Polaris in the camera viewfinder (or OTA eyepiece), and you are now roughly polar aligned and ready to do the more accurate EQ align.
If anyone who needs help setting up the SLT for EQ, drop me an IM and I'll do my best to explain in more detail.
Just remember that it's impossible to balance the SLT mount due to the curve of the fork, so the weight needs to be kept below about 4Lbs to avoid problems with the azimuth motor slipping.
Posted 08 January 2010 - 09:28 PM
I updated my hand controller to SLT_LCM firmware 4.17 to see what Celestron had added.
LCM is Celestrons new lightweight alt-az computerized mount, it's basically an SLT without the curved fork and with a side-offset vixen dovetail.
I found that the SLT/LCM firmware doesn't support EQ align, so I switched my hand controller back to using the generic 4.13 firmware.
Then I saw that NXS 4.18 is the latest on Celestrons server, so I tried that instead.
The NexStar hand controller correctly identifies the SLT mount and the EQ alignment modes work fine again.
Posted 10 January 2010 - 02:12 PM
Posted 20 November 2010 - 07:39 AM
I want bulid eq from my SLT. You can set with SLT and Nikon camera to polaris. Easy because not to long.
I think it's not set right with Nexstar130 to polaris. To long for adjus. I live in North 47Â° 48' 34"
Can you give me idea for set SLT to the north pole.
Posted 21 November 2010 - 08:24 AM
Thats because the motors are at the same position (ie the ota is directly in line between the center of the alt clamp and the center of the az base)
ps It helps balance by offset mounting the eq wedge southerly from the center of the tripod, so that the centre of gravity for the whole mount remains directly over the centre of the tripod, otherwise it will be nose heavy and could topple.
Posted 04 December 2010 - 06:11 AM
My friend made a test with my 130SLT master mirror.
The result: my mirror wrong. You can see in this picture:
I will never buy any telescope in supermarkets!my friend has got a strehl: 0,98% mirror, he made this for himself. He is making telescopes and I want to make my next telescope with him.
Posted 04 May 2013 - 10:23 AM
Posted 04 May 2013 - 12:29 PM
Welcome to CN and to this particular Nexstar forum. :bow:
I'm not sure that I understand your above described procedure, notwithstanding the fact that if you are at latitude 43:26:06, why you are setting your wedge angle to ca. 47 degrees, but perhaps this link might help. I assume that you have by now, found a download to your hand controller which will permit an EQ North alignment ?
This document refers, as you will see, to wedge alignment of the then Nexstar 8i but the principle will be virtually the same for your 130 SLT.
Hoping this helps,
Posted 04 May 2013 - 02:52 PM
Thanks for the link. I have read many other articles on how to perform the alignment procedures. one read if I am at 43 degrees to set my wedge at 47 is why I did that as a trial. it didn't work setting it at my exact latitude of 43 either. SO when my scope is indexed is it supposed to be exactly parallel to the wedge in degrees? I have also heard about setting the encoders to zero and do not see this in your document. I have not tried to perform a drift alignment and do not have the cross hairs for that but may look into it. I have tried to do the polar alignment with the wedge by finding a named star and the slewing to it and hitting undo several times then align, polar align, mount align, this is where my scope drops over 10 degrees below the object and I cannot adjust the mount high enough to get it back to the star as it would then change my wedge angle well over 57 degrees even if I could get it back there.
Posted 04 May 2013 - 05:27 PM
I'm not sure how your wedge is constructed so I can only suggest how you might go about getting a reasonable polar alignment based of course on the assumption that you have no problem viewing Polaris.
1) Firstly you need to make sure that your mount is pointing due North.
To this end you can use a compass or better still, allow the midday Sun to cast a shadow from a pole placed vertically in the ground across the area where you intend to set up your 130 SLT. Once the shadow line is cast, mark it in some permanent way.
2) Take the leg of your tripod bearing the Celestron logo and place it on the line you have drawn setting the other two legs of the tripod equi-distant from the line. (i.e. straddling it).
3) Now take your 'scope and mount, place the assembly on a level, flat surface, (e.g. a table top), and then level the OTA, (in other words such that it rests parallel to the table top or other flat surface you have chosen on which to rest the whole assembly).
4) Now, without moving the OTA at all from its levelled position on the single arm of the mount, bolt your mount to your wedge and then attach your wedge to the tripod.
5) With the tripod sitting on the meridian line you have previously constructed, now elevate the wedge so that ultimately Polaris appears centrally placed in your eyepiece.
You may need to adjust the position of the tripod by pivoting the whole assembly around the "North (logo-ed) Leg" resting on the meridian line you have drawn, and of course, finding the correct elevation of the wedge will no doubt be on a trial and error basis until Polaris appears central in your eyepiece.
Whatever you do though, only obtain Polaris in your eyepiece by movement of the wedge and/or the two, meridian line straddling tripod legs.
Do NOT attempt to place Polaris in your eyepiece by means of an Alt./Az. slew directed from the hand controller.
Hoping these suggestions are of some use to you,
Posted 05 May 2013 - 04:18 PM
Posted 05 May 2013 - 05:27 PM
I hope that procedure helps but you will quite likely have to carry our a few refinements depending on the accuracy of the wedge you have built etc. At the end of the day though and as you suggest, you'd go a long way to beat a good German equatorial mount with GoTo and a worm drive.
That's a great image of M33 by the way ! :bow: Could you perhaps detail how you photographed it, (i.e. 'scope, camera, exposure tim,e stacking and processing software) ?