M42

[Dave Saunders]

Thank's Dennis very much for your helpfull advice, will give it a go next time out, sure it will make big difference.

Regards Dave.

[Dave Saunders]

Hi Dennis,

Got out last night in the freezing cold to try out your star drift idea. I got on with it ok i think, it's much easyier than through the reticle as mine is not iluminated.
I think at first i over compensated and the star was all over the place, however with a little bit lighter touch i got the star to stay (more or less) on the courser. It did after a few minute's drift a fraction off but then drifted back, it seemed to jig around it rather than stay right on it, i wonder if this is right? Anyway i had to give up as the freezing fog had come down and my star that had started in the south had by now drifted almost west.
Regards Dave

[dmill1220]

HI Dave,

IT is important to stay within 5 Degrees of the Meridian and the Celstial EQ, and as close to the eastern Horizon as possible, for the Declination adjustment, again within 5 degrees, if your star drifts past this then find a new one to continue the drift process

Yep! that sounds right!
The jiggling around is due to atmospheric turbulence, and any slight breeze or wind, The left to right dancing around is to be ignored, it's the periodic error that is inherent with all RA axis worm gears.

The key to remember here is, that when you adjust your EQ wedge, you move the wedge, to move that star in the direction of the drift, that is seen on your live view screen, this will involve you making adjustments in RA and Dec with your hand controller to keep it centered in the live view screen in between adjustments.

You must pause for a while between adjustments, what you're looking for is no up or down drift, if it moves up or down but then gets right back on the cursor and its consistent, then its adjusted good enough for the next axis.

Once that star stays consistently on the cursor for at least 3 minutes even with a little back and forth and up and down motion, move on to the next axis. what matters is that you stop the progressive movement of the star up or down, off the live view screen.

Ignore the left to right drift! for each axis!, Once your done, and you install the focal reducer along with the DSI, any tracking errors or PE, will be much less pronounced due to the lower focal length of the Focal reducer.

I use this method to avoid a long drift alignment processes, and to get good goto accuracy, When you goto align your scope with a DSI @ F-10 the accuracy of the goto will be much better, then when you install your focal reducer, it should put most objects in the field of view of the DSI, if not just calibrate your goto from object to object.

Any left to right drift should be repetitive, you will see the centroid drift out then back again. This is OK, with the DSI, it will throw out and not stack any subs that show the drift, since the drift is periodic, the DSI software will discard those subs and not stack them. it has to meet a quality criteria that you have set this is done after an initial average count is performed when you first start taking your images.

I use a count of ten with a minimum of 30% quality for each sub.

It is normal to see the star bounce around a bit at F/10

Dennis

[Dave Saunders]

Thank's Dennis your a real help, there is so much to know,my learning curve is now straight up!! But still it keeps the old brain cell's working,since retiring i needed something to get them working.
When you get time i would like hear what you say about colour with the DSI 1.

Thank's again Dave.

[dmill1220]

Dave,

Look back to the screen shot I posted of acquiring M-13, http://www.extremeastronomy.com/foru...-capture-1.jpg
Hit the Color button and then hit the WB button in the Color control window when you first start.

The key to getting the right color balance is to save your images as a fits file with the save every combined image option checked.

Use the Auto star Envision image processing software for the initial processing.
processing in this manner, You will get and image that is broken down into LRGB fits files.

What you need to learn is how to work with grouped fits files for each color.

I start by opening the Blue Fits as one group, then I examine each sub and prescale the image by adjusting the histogram sliders.

I then throw out any subs that i do not like using the group edit command, it opens a new window that lets you remove the bad subs on a line by line basis in note pad. When your done deleting the bad subs, close the Note pad window and say yes to saving them.

Now I remove any hot or cold pixels, then I Do a two star stack and align, followed by a linear stretch and a log adjustment, brightness and contrast.

I then save that blue as a master blue fits file. I do this for every different sub color and I make master fits files for each color.
What I end up with is a master L a master Blue, a master red, and a master green all in the fits format.

Next I open a New group And I choose all of those master fits files and I perform a two star stack and align.

Next I hit the color merge button I and Choose each individual master aligned fit file for each color, You will see Meade saves that as a Master aligned fit for each color.

Once you have a good color image on your screen you should adjust the gamma first, try a setting 0f 70 % then you can adjust the color balance by assigning different color weights.

It takes a Little experimenting and practice but in this fashion you retain all of the DATA. You can always save the Final image in what ever format your final processing software requires.

Did I loose you?

Dennis

[dmill1220]

Dave,

I couldn't help but notice that you have a picture of your equipment set up on a Wooden deck.

If you plan on imaging do not do it from your deck! this may be why your image is jumping around!. A wooden deck is the worst place to image from since all tiny movements that you make will definitely show up!
Wood Decks will transmit and enhance vibrations from your movements

Dennis

[Dave Saunders]

Hi Dennis,

Yes the floor of my observatory is wood but the pier is steel/cement and go's through floor (not touching) and is encased in sq. mt. of cement so very solid. See post in Observatorys under "My new observatory"

All the best Dave.

[dmill1220]

Hi Dave,

Thats good, I couldn't tell from your avatar that its on a concrete pier.

A very wise setup indeed.
Once you get dialed in, you wont have to worry about it anymore, unless you remove the Mount from the pier.

We have a Huge Titan mount that we mount the Clubs 14 SCT, and The 16' Truss tube Dob that has Zambuto optics on it, it's a very massive concrete pier and slab that goes from way under ground, up 1-1/2 stories to the main Viewing platform.

Last year we had a small Earthquake here in Raymond New Hampshire, it actually moved this massive slab and pier enough so, that we had to re-level and Polar align again.

Let me know how you make out, and if you have any questions on using the DSI to drift Polar align.

Dennis

[Dave Saunders]

Hi Dennis,

Thank's for reply, glad we don't earthquakes around here. Thank's also for info on DSI colour i'l put it in practice next time out. Had hoped to get out tonight to see moon eclipse but forcast is not too good, cloudy!!
I made just as a temp. out of cardboard a star diagonal mask, on first test it seem's clearer than my 2 hole hartman and it didnt cost a penny!!

Could i just ask you one thing about the star you select for drift as i'm not sure iv'e got the right one.
In your post you say " 5 dg. of Meridian as close to eastern horizon as pos. As i live only 50 miles from maridian line to the east would my star then be almost due south

Thanks Dave.

[dmill1220]

Hi Dave,

I'm Glad You now have a better way to focus, I use a three hole Hartmann mask, its done a good job so far.

As far as your first Drift star and the Meridian,
Your meridian is an imaginary line directly overhead that runs from the northern horizon all the way to the southern Horizon, it has nothing to do with your location, wherever you are, look straight up that's your meridian. If you live in the northern hemisphere as I do, the celestial Eq is 90 degrees south of the Pole star Polaris.
to stay 5 degrees within your meridian and 5 degrees of the celestial Eq you can use your setting circles. see attached image

Once you have Polaris aligned in your eyepiece, set your declination circle to read 89.5 degrees, the celestial EQ is now at 0 degrees due south on your Dec scale and it extends from the eastern horizon to the western horizon.

Just remember any drift guide star must be within 5 degrees of both.

When you go to adjust the Declination axis find a star as close to the eastern or western horizon within 10 degrees, but keep the declination circle at + or - 5 degrees from 0, remember your moving the telescope in RA only to the east or west.

Dennis