[Martin Lewis]

That chip size is plenty big enough for a decent all-sky camera and plenty of 180deg fish eye lenses to suit such as the Arecont f2 1.55mm lens. You can see all-sky pictures taken with that lens and a chip just 4.8mm x 3.6mm here; http://skyinspector.co.uk/allsky-camera-ii

Cheers
Martin

[Martin Lewis]

Updated details of the ‘BAA/SPA Advanced Planetary Imaging Workshop’ and the full agenda for the day have recently been posted.

We are please to announce that the following speakers have confirmed; 

• David Arditti (planetary imager and BAA Equipment and Techniques section director)
• Pete Edwards (planetary imager)
• Chris Garry (planetary imager and author of PIPP)
• Chris Hooker (planetary imager and BAA Mercury section coordinator)
• Simon Kidd (planetary imager)
• Emil Kraaikamp (planetary imager and author of Autostakkert)
• Martin Lewis (planetary imager and BAA Equipment and Techniques section advisor)
• Damian Peach (imager and BAA Jupiter section assistant director)

It promises to be a most interesting and popular event so don’t miss out on the limited places available. Reductions for BAA and SPA members.

Details given at; https://britastro.org/node/19008

See you there,

Martin Lewis & David Arditti- event coordinators

[Martin Lewis]

Thanks Andy,
Wonder why it never suggests anything for those field but always for the fields above then?
Thanks for the understanding anyway.
Best wishes
Martin

[Martin Lewis]

Thanks Andy,
That is a very comprehensive reply and very helpful.
Thanks for your testing,

Martin

[Martin Lewis]

That’s interesting. I wonder why some enlarge further when click and for others nothing happens? Curious. Some of mine are uploaded as jpegs and some as pngs- will see if it relates to that.

Thanks for the suggestion anyway, Peter

Martin

[Martin Lewis]

Yes David,

It would be great if it did that but generally the image is hardly any bigger. Why is that one different?

Cheers,
Martin

[Martin Lewis]

Hi Ron,

This is a step I often do to darken the background on planetary images including images of the Ice Giants and particularly images taken in daylight or bright twilight, often Mercury or Venus. I would always do this after wavelet processing as the application of the wavelets will change the histogram distribution quite markedly. You won’t lose planetary data unless it is something very dark like the Crepe ring on Saturn. Removal of the background like this is a simple way of boosting the contrast.

Martin

[Martin Lewis]

As Robin says, a dew shield considerably reduces the amount of cold sky that the lens ‘sees’. Without it the lens will quickly radiate it’s heat to that cold sky and receive little heat from the sky in return. That loss in heat will cause the lens to go below the dew point of the surrounding air and water will then condense on the glass as a result- it will dew up. The night sky typically has a radiative temp in the UK of -10C to -30C. Last night, for example, I measured it as -26C.

The lens will try to reach radiative equilibrium with that cold sky but is prevented from going too low by the heat it receives by conduction from the bath of warmer air it is sitting in and the warmth it receives again by conduction from the scope tube etc. It is  a battle between radiative loss and conductive gain. That is why a breezy night where the transfer of heat from the air is more efficient the battle between radiative loss and conductive gain is more likely to be won. Also reduce the amount of cold sky you see (reduce the radiative losses) and that makes it more likely to stay dew free.

A dew cap does not work by trapping warm air as some books will say.

Cheers

Martin

[Martin Lewis]

 The live streaming worked really well for me and allowed me to enjoy a meeting that I had booked for but was unable to attend. Great innovation which I hope will be extended to future meetings. Thanks to those organising this.

Martin

[Martin Lewis]

Thanks Dominic,

The animation I wanted to upload was showing the small shift in position of a bright spot on Neptune over a 25min period and a side by side comparison just doesn’t compare in functionality to a gif animation.

Still if you don’t have the functionality you don’t have it.

Thanks for the prompt reply anyway,

Martin

[Martin Lewis]

Hi Dave,

I bought a pair for low power views of constellations and they give a big boost to your vision by adding 1.5 mags without changing the size that much- it’s like having super-eyes.

They are simple Galilean design and there is some astigmatism and the quality falls off noticeably away from the centre but they are fun in a dark location, especially for sweeping the Milky Way and looking at large clusters like Pleiades, Hyades etc,

Martin

[Martin Lewis]

As Damian says, now is a good time to get an ADC if you don’t already have one. About the price of a good eyepiece and a sound investment especially if you want to image or view Mars and Saturn from the UK in the next few years.

Es Reid and I did a study of the levels of astigmatism generated by ADCs in use and we found that for a given scope the degree of astigmatism generated by a correctly adjusted ADC is primarily related to the altitude of the object. You can read more about this study at; http://www.skyinspector.co.uk/adcs-part2

I also have a more general page on ADCs those those interested in learning more about these useful devices at; http://www.skyinspector.co.uk/atm-dispersion-corrector–adc

Cheers, Martin

[Martin Lewis]

Thanks Guys, obvious when you know how to do it …..

Martin

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