Merlin66

AstroArtV5 supports the WCS fits header:

The WCS (World Coordinate Systems) is a standard composed by FITS keywords which permit to share the astrometric calibration on many different platforms.

These keywords are written to the FITS header by Astroart when the image is saved after an astrometric calibration, for future use by any other FITS reader which supports WCS. Here is a brief description of some of the most important WCS keywords:

▪ CTYPE1 and CTYPE2 indicate the coordinate type and projection. The first four characters are RA-- and DEC- in case of equatorial coordinates (other coordinate types like galactic or ecliptic coordinates are not managed by Astroart). The second four characters contain a four-character code for the projection type (-TAN).

▪ CRPIX1 and CRPIX2 are the pixel coordinates of the reference point to which the projection and the rotation refer.

▪ CRVAL1 and CRVAL2 give the center coordinate as right ascension and declination or longitude and latitude in decimal degrees.

There are three options for the scale and rotation:

▪ Historically, CDELT1 and CDELT2 have been used to indicate the plate scale in degrees per pixel and CROTA2 has been used to indicate the rotation of the horizontal and vertical axes in decimal degrees.

▪ The FITS WCS standard uses a rotation matrix, CD1_1, CD1_2, CD2_1, and CD2_2 to indicate both rotation and scale, allowing a more intuitive computation if the axes are skewed. This model has been used by HST and IRAF for several years.

▪ The 1996 proposed FITS WCS standard used PC001001, PC001002, PC002001, and PC002002 to represent the rotation matrix but retained CDELT1 and CDELT2 for the scale. It is also read by this software, but should not be used for new WCS's.

Astroart supports both the approximate standard based on keywords CDELT and CROTA and the more precise system based on keywords CDx_y.

Themos,

I use AstroArtV5 which has built-in plate solving....could this be used with your proposed method?

I use one on my NEQ6pro which is fully loaded with a C11, three cameras, Spectroscope etc. Needs 5 x 5 kg counterweights!

It works very well - you just need to make sure ALL the bolts are tight.....

Recommended.

(They only come in Henry Ford Black - I had to repaint mine white to match the mount ;-) )

The "polar" axis, the RA axis, is aligned to the pole using the altitude and azimuth screws on the base of the mount.

If it's aligned, then in theory (!?) the axis can rotate 360 degrees and still be aligned with the pole.

This movement allows you to track a celestial object just by driving the RA axis.....

Hope this helps.

Gina,

I use the Baader T thread locking rings and I think they are only 1 or 1.5mm thick....they do the job.

Guys.

I raised this problem again with Telescope Service who refered me directly to Baader...

Their reply:

""

We made these T-2 rings completely anew recently in 5 different thicknesses (0.6, 0.8, 1.0, 1.2, 1,4) - as injection molded products - to fit international machine standards.

They are being offered as 15 pc set with three rings each per thickness.

This could not be the same units you had received.

""

Problem solved????

Ian,

I had exactly the same problem with a set!

When back to TS and complained...they checked their stock and assured me the ones they had fitted over the T threads!

It seems to come down to the make of the T thread spacers/ adaptors being used - so fine is the clearance....

I ended up cutting them in one place and "clipping" them over the threads....

Guys,

The issue with vaseline etc is that they soften with temperature and like some of the oils and greases can end up everywhere - including on your optics etc etc.

IMHO Don't use them.

IMHO WD40 is not the way to go...the filter clamps/ rubber sheet should separate them...

The moral of the story is to give ALL these adaptor threads a thin wipe of boot polish BEFORE assembly - works 99.99% of the time.

My whole HEQ5 mount, head and tripod has been out in ALL weathers for the past six years - Oz> UK> Belgium> Oz just covered by a green "breathable" patio chair cover.

This covers 95% of the tripod, but I now see the white powder coating is peeling off the feet..would be nice to dis-assemble, shot blast and re-coat them, but I don't think it will ever happen.

Not sure what you mean, but if it's the pillar extension...then I can only say they work very well...give you that extra height with stablility...

I'd still like to see some "real life" astro imaging comparisons as suggested by StuartJPP.

It may well be that the low levels of IR which may be evident in both filters (UV-IR and the Canon) are of no real consequence in Astro Imaging....

billhinge,

I assume we are still talking about a FULL (two filter mod) spectrum mod on a Canon...

The LED results are not unexpected..the wavelength is below the 700nm cut off... for the UV - I can only say the cut off is close to 400nm - what exposures were you using? B to UV?

Tony,

I honestly can't comment on light pollution - it doesn't really exist for spectroscopy.....

I would be interested to see comparable UV-IR exposures with the front Canon filter v's say a Baader ot Artronomik U-iR cut filter,,,,,

Tony,

Those Canon curves are "composite" curves and include not only the "colour balance filter" (LPF#2) but the front anti-alias filter (LPF#1).

I've published more detailed spectroscopic transmission curves...

An easy test would be a camera with only the front filter (LPF#2) compared with an image taken under the same conditions and exposure but with an additonal UV-IR cut filter (ie Baader/ Astronomik etc).

IMHO there's not much difference.

Canon front filter test.pdf

No, no, no.....

Don't use Vaseline, grease, oil, WD40 etc etc. They will either weep with temperature or get onto your optics.....

I've been using the boot polish ( your choice of colour) successfully for the past twenty years.

Highly recommended.

The thickness of a filter in a converging beam adds close to 1/3 the glass thickness to the focal distance.

Snell's law.

The refracted beam is moved towards the normal axis in the glass and hence has a smaller angle to the optical axis, extending the focus....sketch the light path through the filter and you'll see what I mean.

I bought a stack of them for the grandkids (boys and girls 8-12yrs)

before I could even finish telling them about telescopes and how to.........they had it out the box, on the table looking at the Moon , and later Jupiter!!!

Bang per buck - highly recommended.

(I also kept one to pull the mirror out for a spectrascope project....where else would you find a good 75mm/ 300mm mirror for 25 gbp!!!!)

When I de-forked my Lx200 scopes...just loosen one of the fork arms...and the OTA slides out.

The dovetail fits the existing holes - no drilling required.

(The small black "bar" is a safety clamp - which allows you to position and located the OTA on the mount saddle without the fear of it slipping or sliding. Available from Astrodevelopments...their website seems to be down at the moment)

The instrument at the rear ("Ozzie Shiraz" colour) is a Spectra-L200 spectroscope, fitted with an ATik16 guide camera and an ATiK314L imaging camera.

I think it involves undoing six screws and fitting a suitable dovetail....

That's about it.

I use a C11 OTA with a Losmandy dovetail on a NEQ6pro.

Chris,

Thanks for that!

Got it now!!!

I didn't realise I had to Add the custom/home park position.....

I thought I could use the "park to current position" and that would "lock" it in.....

I'm "practising" with the EQMOD simulator to get the scope to "park" to a Defined Position....

I've set the scope to 90 degrees in Az, 0 deg in Alt i.e. the "virtual" tube is horizontal, facing east. I've set this as the "park to current position" and re-synced the encoders.

When I unpark and move the scope I can't seem to get it to re-park at this defined position.....

What am I doing wrong????

I've always used Bob's Knobs as a collimation aid on all my SCT's.

On the 8", 10" and 12" Meade Lx200 as well as a Celestron C9.25.

They do what they say on the lid - work 100% and obviously make collimating that bit safer and easier.

I recently upgraded to a CPC C11 OTA, and once again ordered a set of Bob's Knobs. The website is very clear that different models may have different screw threads (the new C11 has the metric M3 thread) so there's little chance of buying the wrong sized knobs.

When the knobs arrived, they fitted OK but with the Fastar cover plate on the secondary there was insufficient clearance between the knurled head and the surrounding plastic - you could just get your finger tips into position - with difficulty...(The notes say that the reduced clearance between the bayonet cover of the scope and the Fastar plate limit the available height...)

I raised my concern with Bob and he was fast to respond...we discussed the possible options and he agreed to make up a couple of sets of "specials" to evaluate. He sent these to me no charge.

Well, they arrived....

The M3 x 25 option worked perfectly and still gave enough clearance to fit the bayonet cover.

The head of the knobs are now clear of the Fastar cover and can easily be turned between the finger and thumb.

I couldn't ask for better service, understanding and response.

I like to thank Bob for his quick reaction and ability to develop a more robust solution to my problem (and hopefully others with a similar scope)

Well done Bob!! A great supplier to the amateur astronomer!

I was just doing the "annual" check, cut and polish on my eyepieces ( see message #25 above) and noticed the foam is falling apart....mind you it must be almost thiry years old! Looks like I'll have to get a replacement foam inner and get the 1 1/4" wad punch and exacto blades out again....

That's OK - so am I - an exile from Oz -

Basically just make sure there's a degree of out of balance on the Dec axis at all times...this may mean sliding the OTA up/ down in the holding rings or by adding say a Tesco velcro wrist weight to the tube - the idea is to have a "load" onto the Dec axis.....

HTH

bamus,

re-read your message....

What you are saying is that the mount, not the guide set up is allowing movement in Dec:

With guiding with DEC turned off I got 3 to 4 minutes perfect tracking and then out of nowhere dx/dy graph starts sharply moving from middle line

If your PA as as good as you say, then it's got to be that the dec axis is going "sloppy"..

the usual fix is to pre-load the dec axis ( some out of balance load) so there's no need for reversal/ dead band.

What do you think??