Di electric Diagonals useful for imaging ?

[AztecastroMcJ]

thinking of adding some equipment to try improve my viewing and imaging with my 127mm Mak and unmodded colour webcam,

would di electric diagonal be usefull for imaging planets and moon with webcam ?

noticed most good scopes seem to have these fitted as standard so i'm guessing they must b better ?

intersted in 1.25 SW one @£54 seems good value upgrade ?

also wanted quality red filter for moon, only one i found was astronik's red filter @£66 it's bit too much for me

noticed Neodymium Filter @£40 which supposedly gives better views of planets and moon aswell as dso's and said can be used for imaging with UV/IR Filter which i have

would this be good choice or should i go for something else ?

any suggestions

help, advice appreciated

James

[brianb]

You do not need a diagonal for use when imaging. Your camera won't get neck strain. If you need something to use up back focus distance, a plain extension tube is best.

For imaging with a colour camera, the only filter you should even consider is a UV/IR blocking filter (which is definitely useful).

[AztecastroMcJ]

thx Brian, if i use my current 2x Barlow without diagonal what ratio would Barlow be working at ? would it be a bit less like 1.5x ?

so far i always used webcam with my barlow and diagonal attached

when webcamming moon i use with BW setting on

would any filter help with this ? (red filter seems popular)

thx for advice help James

[brianb]

In my experience, 2x barlows with the camera stuffed straight into them are usually a bit more than 2x.

The "monochrome" setting on your colour webcam does not remove the Bayer filter, it just averages out the signal across groups of 4 pixels (2 green, one red & one blue). If you add a red filter you're removing the signal from 3 of those 4 pixels. If you want to get the red signal it's at least as effective to use the camera unfiltered, in colour mode, & seperate out the R G & B images in software after processing ... no extra light losses in the extra filter, and the data in the other layers may help with alignment etc. during processing.

If you want / need to make images in single colours, sorry but a monochrome camera is a much better tool for the job.

[AztecastroMcJ]

thx again for advice

monochrome cam is on my ever increasing list of future purchases

alongwith maybe dslr,

cooled ccd,

new mount n larger aperture scope and

solarscope (pst) which shows sun's prom's

lots to save up 4 then

thx

James

[AztecastroMcJ]

Brian meant to ask if u use di electic diagonal ?

[Space Cowboy]

Doesn't the star diagonal add 1.5x to the barlow. I think without the diagonal the image is slightly sharper if your still using the bog standard diagonal supplied with the scope.

[brianb]

For imaging - the only diagonal I use is the one built into my Lunt CaK narrowband filter (or rather the filter assembly is built into a diagonal). Everything else is "straight". Visually I usually use an erecting prism diagonal which makes comparison with charts easier (no horizontal flip) - sometimes I use a dielectric diagonal for viewing planets as the image is a bit better than the prism diagonal, but for objects at moderate altitude (e.g. Saturn this year) I prefer not to use a diagonal at all.

With Barlows, the relationship of magnification to back focus depends on the design of the device, some manufacturers (Televue) give you a chart showing the effect. Actually I have never used a barlow between the scope and the diagonal ... I don't use barlows visually & I don't use diagonals for imaging. Except the Lunt diagonal which won't fit into a barlow because of its length.

HTH.

[AztecastroMcJ]

yes thx

THA

cheers