Light polluted skies

[leon]

Good Morning to you all, but i suppose some of you may read this in the arvo

Anyway, i would like to ask this.

Last night i had a go at imaging the Horse Head nebula, and at 3 minutes at 500 ISO it was pretty obvious that the city lights toward the east caused considerable build up on the image.

The horse head neb in itself is fairly faint yet there are also some very bright stars in that same field of view.

How do i go about capturing this creature, do i shorten the exposure at a higher ISO or do i reduce the exposure time and at the same ISO as earlier, and take more of them.

Or do i wait till the object is more Westerly and in darker skies, so to speak.

Could some experienced person please assist in what would be the best way to go in regard to time and ISO setting on fainter objects when the light pollution is not that good.

I would be using the Takahashi 106 and the Canon 5D, also the Tak has a Hutech LPR filter behind the rear lens, this dose help a lot with Light pollution, but Im sure there is a limit until there is a gradual build up.

Any suggestions would be greatly appreciated.

Leon

[JohnG (John)]

Hi Leon

Sounds like you might have to do some experimental shots at various lengths and ISO's to find your sky fog limit.

The last time I did the Horsehead I managed to get 600 second exposures at ISO 800 but that was in my dark sky location:

http://www.pbase.com/takman2/image/71256604/original

The Tak 106 being a fast instrument, you might be able to get away with 5 minute exposures, if the sky fog becomes too degrading then I think you may have to wait until the object is overhead then have another go. I would experiment with various exposures though.

Cheers

[Alchemy (Clive)]

im not sure nof the transmission range of the hutech lpr filter, could you use an Ultra high contrast filter , or one of the line filters Halpha 13nm and 6 nm ranges( expensive i know) both come in 2 inch

I visited ezy styles recently and he showed me some full res shots he did in his suburban location .... brilliant ones too .... including the horsehead. he uses a uhc filter and it worked for him.......

The tak 106 ...can you frame it to miss some of the brighter stars

[leon]

Thanks John, yes i did consider the fact that the horsey was still a little low in the East, and that surly makes some difference, you could be right, it might be best to wait until a more vertical, or even Westerly position in a month or so.

I just get a bit excited when all these stars are out and cant seem to wait.

Alchemy, although the suggestion you gave about filters is a good one, a selection for the Tak can be quite costly.

The filter size for the Tak is 72mm, and screws into the rear cell of the scope, so to purchase one that size runs into many hundreds of dollars.

The 72mm, and the 77mm I bought for the Tak, and my Canon camera lens some time ago from Hutech in the States set me back nearly $900.00 delivered.

However thanks for your suggestion

Leon

[Gama]

You need to use a filter, from memory (Dont take it as gospel) i think it was H-Beta, but you can check easy enough...
This should darken most of the background and allow a better exposure to occur.

Theo