6" Dob any good for DSO's ???

[spaceboy]

What's the vote? I have recently had a 130P F/5 which I found did surprisingly well on DSO's but the 6" dob is F/7.8 which is great if you only have cheap EP's but isn't it a little slow for most of the larger deep sky stuff being better suited to planetary observing ??? From my experience I have also found slower scopes to give much duller views compared to faster scopes despite viewing objects with similar exit pupils.

Any input would be appreciated.

[MjrTom]

The ~1200mm focal length of the 6" is a bit long but I manage nicely with my 1000mm refractor as long as you have a decent 2" eyepiece for the bigger targets

I can still get the double cluster completely in the FOV with a little space to spare.

Most average sized dobs tend to be around 1200mm focal length.

Not ideal but workable I would say.

[spaceboy]

I thought as much

I would have been happy sticking with the 130P TBH but those AZ mounts they come on are too flimsy for my patience and the EQ mounts combo dosen't look that much better. I wouldn't mind but I think they sell the OTA only else where just not in the UK ????

[Peter Drew]

There's no reason why a 6" Dob should not be suitable for DSO's even at around F8, the main difference with a short focal length will be the wider field of view with the same eyepiece. Theoretically, at the same magnification, the image brightness visually, should be the same on either. The darker background and better edge of field characteristics of the longer FL can often give a more pleasing view of many DSO's. John Dobson often bemoaned the fact that builders were using too fast optics in his unique construction.

[spaceboy]

Thanks Peter. You just brought to my attention another problem. I would need longer FL EP's. Oh well back to the drawing board :(

[MjrTom]

Whats the longest focal length eyepiece you have?

Whats the largest object you want to view?

[spaceboy]

The 21mm Baader with the 1.25" lens removed gives me the equivalent to a 2" 32mm EP. Would at least want to fit the witches broom in and double cluster (not at the same time obviously )

[MjrTom]

That should give you about 1.7 degrees true filed with the 6" dob.

This will be a little tight to get both clusters in view but not far off it I would think.

[RikM]

The Double cluster fits nicely in my 20mm 70° EP and 1200mm FL Dob. You should be fine with that.

[MjrTom]

Actually looking at the size of the double cluster my first comments are not quite accurate its the 24mm 68 degree eyepiece which fits it perfectly.

As rik says should be no problem at all.

[spaceboy]

Thank guys but having just took a ride out to look at one the focuser was found to be the old R&P type. I was under the impression all the later models had been upgraded to crayfords. I know the F/5 explorer has. Looking like it's not going to tick enough boxes so didn't bother. Thank for all the help though guys

[swamp thing]

Nick.

What about the 6" OTA.

First Light Optics - Skywatcher Explorer 150P OTA

This is a faster system. You could knock up your own Dob mount for it.

That would be a lovely RFT

Regards Steve

[spaceboy]

Thanks Steve. I had considered doing this for my 8" newt but think I'm now going to stick to my original plan of getting a giro mount for my CG5 tripod. This way if I chose I could always mount both the C100ED & 200P, the 100ED alone for a grab and go 'ish set up or 200P for star parties. Just finding someone who has a giro III for sale as I have not had much luck snapping them up in the past (Mark and Stu ).

[MjrTom]

Sorry Nick!

They are definitely worth getting hold of, I would not part with mine.

[Mr Q]

As far as a 6" suitable for DSOs, I used a 4" newt in only somewhat dark skies and had no problem detecting (visually) objects down to 11th mag. near the zenith.

As for short vs long f lengths, the above posters have covered that issue well.

[Moonshane]

I can fit all but the largest DSOs into my widest eyepiece on my 16" dob (giving about 1.1 degrees). For those that don't fit I look in my finderscope! The double cluster covers only about 1 degree so it easily fits into this and the withces broom is no problem at all.

But seriously, I have have a 6" f5 and a 6" f11 newt and they both perform well within the confines of a 6" scope. The f11 is certainly better on planets etc but both are decent and both show broadly the same image at the same mag as mentioned above. As you have the 8" f5, I'd be tempted to be patient and buy the used Giro. They do come up every now and again. My giro 2 works a treat.

[spaceboy]

I found that Giro mounts are like buses. Not 1 for ages and then 3 come along at once. Trouble is when

I was on the fence regards the 6" dob anyway but then finding I'd be having to deal with a sloppy R&P focuser put the nail in the coffin on that idea. OK I could upgrade the focuser. The trouble is to fit a crayford you have to chop a bigger hole in the OTA as a crayford is larger and then you have to cough up for an adapter so it fits the slimmer OTA.

[Tribal-Wolf]

There is/was a 150P skyliner on ebay today for £100, that is a gift at that price.