I think I screwed up !
Posted 07 February 2008 - 02:57 PM
Having said that there's one thing I always feel the Met Office fail to do with all their hi-tech equipment and know how and that is to look out of a window occasionally !
Good luck then with any viewing you might get in and don't forget, pay particular attention to those antibacklash settings! The watchword is smoothness, small delays in movement permissible and remember that the altitude axis is very sensitive to this aspect.
Posted 08 February 2008 - 08:44 AM
With respect to your alignment technique, I found the accuracy of my alignments shot up by using a two ep technique others advised. Use a low power ep (e.g., 24mm on my 8SE) to initially center an alignment star (I use the defocused donut method to improve centering) then hit 'enter'. Now switch to a high power e.p. (e.g., 6.7mm w/an 8SE), center the donut, and hit 'align'. If you do that with both stars, and use the same final approaches to do the centering, you're alignments will be much better.
Posted 08 February 2008 - 11:30 AM
I don't know, but when you referred to Cenk's "alignment technique", might you have been speaking of the thread I recommended to him which I wrote for the "Alignment Tips Here" -- "Sticky" ? If so, you are absolutely right in my opinion to advocate the use of two EPs although there were two mitigating issues perhaps to consider when I wrote those tips.
In the first instance, I was writing for someone in particular and perhaps even for those in general who were having difficulties in "hitting" a 20mm EP at all so the idea was to bring them at least "on track" so to speak. If they then refined the accuracy as you have detailed then that's the real way, I certainly feel, to go.
But now to the second instance. If I'm honest with myself and I try to be so, I'm too lazy to go into that much detail. I know from practice, I can get any object within a 20mm EP after alignment so if I need to centalise it, I just do that ! If. on the other hand, I want to Barlow the object or change the EP to one of shorter focal length, then I also just make sure the object is centralised before the swap. I therefore forget alternative and more accurate ways of aligning as you have kindly reminded me !
Please ignore me though if you weren't referring to that specific thread of mine but if you were, then that's my explanation.
Also, many thanks for the "tip" ! Senility's creeping on I'm afraid !
Posted 08 February 2008 - 11:59 AM
Posted 08 February 2008 - 01:07 PM
Sounds like you're ready to go tonight and it looks like it might be a good one down here in the South East corner!
If I think I know what you mean, go into the menu on the HC. Find 'Scope Set Up". "Enter" and scroll down till you get to "Goto Approach". Set both altitude and azimuth "GoTo Approaches" to positive.
Now make an Auto Two Star Align (Don't forget UT time and American format date). You must then select the first star, slew manually to it, find it, put it in your EP and centralise it. (Don't forget the "Doughnut")!
In centralising it, make "Your Final Approach, that is moving it to the centre of the EP using only the "Right and Down" directions. If you overshoot, go back however you like, BUT make that final approach, "Right and Down" !
Now having "Entered" and "Align-ed" the first star, choose the second. Whatever your choice, the OTA will now slew automatically to it. Just repeat the process as for the first star, hit the "Enter" and "Align" buttons and you should have now completed the task.
When you then "GoTo" objects of your choice, to ensure the best tracking, use the "Right and Down" buttons if the object is between North and South on your Eastern side, and "Up and Right" if between North and South on your Western side.
Hope this helps,
Posted 08 February 2008 - 02:10 PM
Skies look lovely here. Scope is already setup, powered and been cooling down for about 1 hour. Even taking my Macbook with me tonight with Starry Night Pro Plus ! Will try the Right Down method straight away. Will post back.
Posted 08 February 2008 - 02:47 PM
I'll keep my fingers crossed for you that all works well. However, you might need to play with that "GotTo Approach" setting, if things are not satisfactory, by swapping to a "Negative Altitude Approach". The "Azimuth Approach" must, under all circumstances, be left on positive.
If you reverse the "Altitude Approach" you will then have to modify your "Final Approach" to "Up and Right".
The other aspects which will affect your centralisation and tracking objects in particular are your antibacklash settings.
Have you worked on these yet, because if they are not satisfactorily set, they will for sure, influence your overall "GoTo" performance ?
Best regards and good luck for tonight !
BTW. My guess is that it will perform satisfactorily with a positive "Altitude Approach". Perhaps however, one thing to bear in mind is that if you do think you have to vary anything, make each variation one at a time and test. Otherwise you might be unfortunate to lose track of what you've done.
Posted 08 February 2008 - 02:54 PM
Posted 08 February 2008 - 03:31 PM
Well I think tonight is going to be a learning curve exercise, maybe for both of us but --- first and foremost, I need to know exactly what you are doing and what settings you have overall.
1) Have you set the GoTo Approach to positive on both axes?
2) When you slew back and forth or up an down moving an object in your EP, is the movement smooth at speeds 5 and below ? (Antibacklash settings --figures for both axes?)?
3) What size EP are you using to align ?
4) Which stars are you choosing ?
5) What power supply are you on at the moment ?
6) Which alignment method are you using ?
Sorry, Cenk, I will indeed try to help you but I really need to know where we are both starting from. In any event I think we have to sort this one out first before you can go "swan-ing" about the sky !(LOL).
Posted 08 February 2008 - 03:31 PM
Posted 08 February 2008 - 03:51 PM
Additionally while your time and date seem to be right (guessing) from what you've said about only being "a few degrees off", (although how far is a few ?), are you using Lat. and Long. or are you set to a City/Town etc. If Lat. and Long. are these correct ?
Posted 08 February 2008 - 04:29 PM
I got really frustrated and packed everything back up now ! Basically, all is as you said, set to positive. I used Lat/Long based on what my Blackberry GPS told me. SOmething like: N51:00:48 W0:05:01. The only difference is that the Nexstar asks for W0:05:01 first, the the N51:00:48. Time is correct by a few seconds. Date is def right. I am aware of UK/US format difference. I tried the 3 star Auto Align and the 2 star Auto Align choosing a whole range of different objects. Mixture of, Polaris, some of the bright stars of Ursa Major, Betelgeuse, Rigel, Saturn, Mars, Castor, Pollux, Sirius, Procyon, You name it I tried it. It sometimes gets one object into view, but then completely looses it.
When I say off by a few degrees, I mean something like, I would tell it to go from Betelgeuse to Mars, and Mars would be 3-4 cm out in the finder. Sometimes I get 1 cm sometimes 3m. Rarely in FOV. Obviously I can see the object to can manually align and look at it. But if I tell it to go find something faint, I will never find it. I obviously don't know how accurate this is supposed to be but I sure expected to see a few more objects at least within FOV of my 35mm Televue.
Posted 08 February 2008 - 05:44 PM
Sorry you felt you needed to end your session but please rest assured, you're not the first to feel frustration with these GoTo 'scopes. They do work, and work well, but they do have to be set up correctly.
Anyhow, from what you've now given me I do have a better idea of what might be happening but of course I may still need to ask for more data.
Reviewing then and from my understanding of what you've given me, your GPS puts you around the area of Haywards Heath. No names, no pack drill of course, but it would help if you could confirm that you essentially match the data the GPS is telling you. (To be honest, if you're within a 70 mile radius of Haywards Heath your Lat. and Long. should be fine).
From what you've said about "even if you have an object in view you rapidly lose it"; may I ask whether the object "slips" suddenly with a jerky movement out of the FOV or is it a slow "slip", perhaps caused by inaccurate tracking?
From what I'm hearing though, it sounds to me like one problem here is the antibacklash which may still be incorrectly set; (possibly compounded by other aspects that are equally not quite rightly set or complied with.
My advice at the moment therefore is to sleep on it but do come back to me on the points I've made.(I need all the information you've got about what's been done in setting your antibacklash and what the settings are if you can provide such).
Give me also a little time to think about it and I'll try to design some sort of flow chart to take you through the whole procedure step by step if you think that might help.
Posted 08 February 2008 - 05:53 PM
Thank you very much for your help with this. I really appreciated it. Yes I am near Haywards Heath. I probably didn't explain myself right above. The objects, once in FOV are fine, they are tracked and all seems good. The problem is, once my alignment is complete, I can find my first object, which is within the FOV somewhere. When I then move to my second object, this is about 1cm-3cm out from even the Finder, let alone the FOV through the EP. Obviously moving to 3rd object is ever more out and moving to my original alignment stars, these are out too.
It sort of slips out of alignment very quickly after the first object. Some of my alignments would not even find the first object selected.
The main reason why I stopped my session tonight was more the Dew than the alignment. I have ordered myself a Dew Shield and should be ok next week. I do want to get this alignment problem out of the way first though.
Posted 08 February 2008 - 07:03 PM
I couldn't resist it and just went out again. And guess what it worked this time. Everything almost centre. The settings this time were, I used London instead of my coordinates, I used the 25mm EP, there was now Dew :-)
Strange. Is it luck ?
Posted 08 February 2008 - 07:11 PM
I think I've now got the basic picture although I'd still like to know how you tackled the antibacklash settings. Did you check out those you have in daylight ? ( A procedure which will certainly put you in the right ball park if not create absolutely useable antibacklash settings for nightly sessions.
If it's any encouragement, I did my normal Auto Two Star Align tonight on my N8i using Betelgeuse and Polaris, sighted in my 20mm EP and then centralised by robbing my 9X50mm finder of its 26mm crosshaired EP. Results have been good. I have no reason to doubt that yours will soon be following suite!
As to settings, (I think you can read across from my N8i to your N6SE). I have my GoTo Approach" set to positive on both axes. (Positive takes advantage of the fact that the N8i is originally backend heavy).
If however you think your 'scope is neutral or nose end heavy, then a negative altitude setting might suit it better, (don't forget though that the azimuth setting must remain positive).
Trial and error testing I'm afraid but once you've determined which is best, then its pretty well set for life !
Next, regarding antibacklash, this is a feature which seems to be individual to the scope in question, but in general I think concensus of opinion dictates that the altitude might well be kept under "10" for both positive and negative settings, while the azimuth is set high, 80 -90, (although in any event, the azimuth axis is nowhere near as sensitive to backlash as the altitude.
What are your current figures? Are they factory settings or did you test and set them? Is there any jerkiness in the movements of objects within a given EP when you move said object.
Initial food for thought?
Posted 08 February 2008 - 07:15 PM
What did I do the first time? I have no idea.
Have fun with your scope.
Posted 08 February 2008 - 07:23 PM
Good to hear that ! I was writing the above while you were testing and posting !
Don't know about luck, but you will need to determine whether it's repeatable. However, it sure sounds as if "London" might have cracked it so maybe the GPS co-ordinates are wrong although from what you told me they seem to stack up ! Perhaps check "London" against the GPS then you'd know exactly what was happening here.
If you can get it to align consistently, then I reckon you're 90% there and that the other 10% will be down to honing all settings.
Good luck and well done ! Patience rewarded !
If I can help further let me know. I'll always try,
BTW. Don' forget that hairdryer to dispel the dew ! (Careful use mind ) !
Posted 09 February 2008 - 04:05 AM
I matched up the coordinates of London with mine and it looks like I my coord's right. Not sure what is going on. I will try again tonight and post.
Posted 09 February 2008 - 04:07 AM
Posted 09 February 2008 - 05:49 AM
Cleaning the corrector.
The first rule is, as many have advised, --- "Don't" --- unless you consider it absolutely necessary !
If however you do decide to clean, make sure you thoroughly read through Mark's very descriptive advice on how to do it : likewise the links provided on and since, you opened this thread. Make sure also that you've got all necessary materials at your fingertips.
Also a note in passing: I personally don't like the idea of using a compressed air can, because I always feel it can introduce unwanted moisture on to the plate, preferring myself, to just brush the dust away lightly with a lens brush. (a clean ball "puffer" is also however, satisfactory in my view). Others may of course disagree over my non-use of compressed air. In any event and whatever you use, take your time over the job and work very carefully.
If the settings are "Zero" all round, I feel sure that the 'scope could certainly benefit from some "tweaking".
This is a job you can undertake indoors, in broad daylight merely by pointing your 'scope out of a window and aiming at an object like a street lamp, telephone line insulator or, if you wish, (and I've found this useful as it provides a grid pattern) a brick wall. The main thing is , is that the object can be focused.
Approach the task, one axis at a time and one setting at a time. Concern yourself with slew speeds 5 and below. Higher slew speeds will take care of themselves.
Bearing in mind others may well have other ideas about this, start say, with the Altitude Positive setting (to be found on the Menu followed by Set Up Scope followed by Antibacklash). Set the rate initially to slew speed 5.
Centralise you object (or find a place to start on a brick wall). Press the "Up" button to elevate the OTA. Note whether it's smooth or jerky in its movement, (at "5" movement will be relatively rapid). If jerky, adjust the positive setting until smooth. If there is any delay before movement begins, pay no heed to it. Smoothness is what you seek. (There should be little delay time at slew speed 5 but you might well find delay time increases as the chosen slew speed is reduced --- no matter however, always go for smoothness of movement).
Return the OTA to the original position after each trial setting and also note any jerkiness on this return journey.
Now move progessively to lower speeds, 4, 3, 2 (don't worry about 1). Repeat the procedure until you have a smooth acton in Altitude at all these speeds with a positive setting. Now repeat the process switching to the Altitude negative setting.
When you have a smooth action in both up and down directions, move to the Azimuth positive, repeat the same and then finalise on the Azimuth negative. You will I'm sure, find that the Azimuth axis is far more tolerant of changes than the Altitude axis.
You should be up and running with a satisfactory setting within half an hour to an hour tops ready to get out there again tonight ! The forecast is good !
Hope this helps, and happy slewing !
Posted 09 February 2008 - 05:58 AM
What sort of values or tweaks am I looking at ? Increasing values by 1 or 10.
Posted 09 February 2008 - 06:27 AM
No I would think "10s" and possibly "5s" basically, "Tweaking as you go" ! It really is "try the water, trial and error, hit and miss" here when it comes to backlash settings but that's roughly the order of magnitude.
For what it's worth my settings are about 5 on both Altitude axis settings and about 85 -90 on the both Azimuth, BUT remember, each scope is different so you have to decide on the best settings for yourself. All I can say therefore is perhaps aim for low Altitude settings and a high-ish Azimuth.
BTW. If you haven't seen it, Mike Swanson's admirable web site is full of Nexstar information, including antibacklash.
Mind you, he and I differ a little over our individual approaches to antibacklash !
Posted 09 February 2008 - 09:01 AM
Posted 09 February 2008 - 10:05 AM
I gave that a go. If I increase the number to much, there is a big jump from up to down and left to right. The scope just moves a large area really quickly. This obviously is not very desirable. Is this to be expected ?