Merlin66

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??

Double check your polar alignment - if the mount has good PA then there should be no need to make correction in Dec...

A slight out of balance -to the east for RA, either for Dec will help maintain worm/ wheel contact. Doesn't need much.

HTH

Darren/ Gina

Would heavy duty shelf brackets work?

There will be some support against spreading due to the extended edge on the roof.

(On my last 3m x6m ROR I was using 20mm hollow square tube for the roof frame....)

I asked my wife (the extreme tester!!) to take some shots around the garden with the 450D and then with the modded 1000D (CWB set)

When I mixed and presented the results she couldn't tell the difference. Colour and focus - close-ups and wide were very acceptable.

So I'd have to say that the majority (ie family) won't notice any problem.

Good question!

In the older models pre 450D the filter removed was 3mm thick and this caused a shift of almost 1mm in the focus. I could not get a standard lens to focus on a 300D with the filter removed.

On the new cameras the filter is only 0.8mm thick so when it's not there the focus point will only change by less than 0.3mm.

If anyone has a "filter removed" mod they can confirm AF still works.

(My 1000D was claimed by the seller to be "filter removed" - I can focus very well with the AF - but I don't know of anyway of confirming the filter has actually gone -other than stripping the camera - which I don't want to do. I was hoping that the spectroscope tests would show an extended coverage out into the NIR but this was not the case!)

Guys,

You should be aware that even when the "filter" is removed the dust shaker filter left behind acts as a UV-IR cut filter.

I have done some tests with a stock 450D and a "full spectrum modded" 1000D and the spectroscope definately shows the cut-off.

So, if you mod a camera you definately don't need an additional UV-IR filter.

Simple Ha filters for solar observing just don't exist!

The very narrow bandwidth required (<0.1nm) means that you need to use etalon type filter which costs $$$$$$.

The cheapest source of an Ha etalon is the Coronado PST. The etalon can be used with a suitable energy rejection filter (ERF) on the objective and the PST etalon positioned infront of the focus.

This set up say on an 80mm scope would cost around 800 gbp on top of the cost of the scope!

I've used the 8" , 10" and still have the 12" Lx Meade.....

but I've got to say the C9.25 has won my heart....

The size v's weight is very good and sitting on the NEQ6 it just "looks right!"

I've had no issues with mirror flop etc using it for spectroscopy with 25-30 micron slits...it's a very good work horse...

If I didn't have the 12"Lx I'd be seriously interested in a C11... but that's another story......

The image is incorrect, but the description is correct. It would work very well!

Easily done... works reasonably well.

You can use a Mogg adaptor (google) which fits your lens and has a end attachment for 1.25" eyepieces and/or cameras.

I used a x2 camera extender and removed the guts; replaced them with a small piece of 1.25" tube. Now I can use any eyepiece on any of my old Zuiko lenses.

Watch the back clearance on the lens! The backfocus is 50mm but some lens have a rear element which slides back into this space during focusing...one of my 50mm lens only allows 30mm clearance.

When running WcrMac did you have a capture program like Craterlet running AT THE SAME TIME??

This is required.

Kev,

The backfocus for the Canon is exactly 44mm.