Big Newts for Visual

[DRT]

I have a 12" Dob and a 6" Newt and love the views through both, but the Dob frustrates me because it is so heavy and I don't find the viewing position too comfortable and the Newt frustrates me because the images are so small.

I also have a Giro III mount on a 16" pillar on top of 2" stainless steel legs. A very solid foundation for heavy gear.

I am thinking of buying a Skywatcher Explorer 250PDS or similar to sit on the Giro III, presumably with a couple of sandbags hanging off the other side to keep it all upright, so that I can have the big aperture experience with the convenience of the Giro mount.

So my question is: are these big fast Newts any good for visual or are they really just for imaging?

[ronin]

First they are all newtonians, John Dodson developed an inexpensive base to put a newtonian on, he did not develop a scope.

A fast newtonian will need a coma corrector and since the mirror is the same lump of glass it will need a big mount. Any breeze and wave bye-bye to that exposure.

If I recall the PDS bit is (or could be) simply a lower profile focuser, as that is all that the 200/250 needs to get a DSLR to achieve focus.

[Moonshane]

Hi Derek

There's no reason a pds would not be perfectly good for visual observing. A slightly over sized secondary will have a small effect on contrast but not worth worrying about.

Is your dob a flextube? Could you not move the position of the uta slightly?

I find a 45° angle best but many scopes don't seem like this.

[swamp thing]

Why not build your own Dob base that is lighter and at a more convenient height for you?

The particle board used in commercial scopes is heavy and well......garbage.

[DRT]

Thanks, ronin.

I know that both are the same style of scope but it is the operation of the Dob mount that I find frustrating at times, particularly with low targets.

My Dob is f/4.9. The 250PDS is f/4.7. So my question is really about whether or not that little difference in speed will dramatically affect the scopes ability to be used as a visual instrument.

Coma doesn't bother me too much as I tend to use these scope to look at planets and the moon and it is only when I point it at stars that I notice the problem. That said, a coma corrector would be fine if needed.

[scarp15]

Do you use an adjustable observers chair whilst observing with the 300p? I find the ergonomics to be just right.

[John]

I used to use a 10" F/4.8 Orion Optics newtonian on a Giro-type mount. It worked pretty well and the eyepiece could be at the height I wanted because of the adjustable tripod legs. You need a pretty solid tripod though, I found the EQ5 steel one not as stable as the 2" steel CG5 one.

My 12" dob is F/5.3 and with the custom "Moonshane" dob mount the eyepiece is at a comfortable height for observing when standing, which is my preference.

[DRT]

Why not build your own Dob base that is lighter and at a more convenient height for you?

The particle board used in commercial scopes is heavy and well......garbage.

You are just trying to tempt me into the lair of the Dob Squad so that you can assimilate me

Hi Derek

There's no reason a pds would not be perfectly good for visual observing. A slightly over sized secondary will have a small effect on contrast but not worth worrying about.

Is your dob a flextube? Could you not move the position of the uta slightly?

I find a 45° angle best but many scopes don't seem like this.

Thanks, Shane. I'm not really comfortable messing around with the optics and it is really the height that is the problem rather than the angle of the eyepiece. My garden is surrounded by houses and trees so I need targets to be quite high in the sky to get my Dob pointing at them. Mounting a large Newt four or five fee off the ground would increase the amount of sky I can get at quite dramatically, which is where this idea is coming from.

And for the Dob Squad, Part 2 of the plan is to upgrade to a bigger Dob

[Charic]

DRT....can you raise the Dobsonian, by using a water butt stand, for your horizontal viewing, remembering that the more horizontal the view, the more atmosphere your looking through, with the associated problems of unstable air currents?

I too have properties and trees at my location, but I'm fairly lucky in that Ursa Major and Cassiopeia  pass right overhead my garden?, so most of my targets are in my Zenith, this helps to avoid the  direct street lighting, and the depth of the atmosphere on the lower targets. Without first knowing it, these obstacles that I thought were a hindrance to my skyline - horizon views, are actually a bonus in directing me to targets almost straight up.

[DRT]

Yes, straight up is where my Dob normally points

I thought about sitting the Dob on a platform but that just adds more weight and hassle. I don't go for horizontal targets for the reasons you mention but the lowest (roof) horizon in my garden is directly south so the planets pass across from left to right, sometimes just above the roof line or even between the gaps between the houses. If I can get a scope pointing at them and the seeing is fine they are high enough to get a good view without too much thick atmosphere. If the houses were not there they would actually look quite high. Unfortunately, the Dob just can't get to those bits of the sky, but my 6" Newt on the Giro can, which is why I have had this thought.

As a specific example, at 6 a.m. this morning I was out looking at Saturn with the 6" Newt. My neighbour's TV ariel was in the FOV. Have a look at Stellarium to see how that compares to your man made horizon

[Charic]

Yes, straight up is where my Dob normally points

I thought about sitting the Dob on a platform but that just adds more weight and hassle. I don't go for horizontal targets for the reasons you mention but the lowest (roof) horizon in my garden is directly south so the planets pass across from left to right, sometimes just above the roof line or even between the gaps between the houses. If I can get a scope pointing at them and the seeing is fine they are high enough to get a good view without too much thick atmosphere. If the houses were not there they would actually look quite high. Unfortunately, the Dob just can't get to those bits of the sky, but my 6" Newt on the Giro can, which is why I have had this thought.

As a specific example, at 6 a.m. this morning I was out looking at Saturn with the 6" Newt. My neighbour's TV ariel was in the FOV. Have a look at Stellarium to see how that compares to your man made horizon

Not sure i understand the first sentence about the weight? and a 'butt' could give you about 60c rise in height! http://www.diy.com/departments/sankey-polypropylene-water-butt-stand/195284_BQ.prd?gclid=CNzGqbLIssMCFUPJtAod1DAAGg&ecamp=SEAPLA195284_BQ&ef_id=VLXV9gAABOl8FNot:20150126210723:s

Could this small rise in height achieve a little more reach / field above the roof line?

[DRT]

Not sure i understand the first sentence about the weight? and a 'butt' could give you about 60c rise in height! http://www.diy.com/departments/sankey-polypropylene-water-butt-stand/195284_BQ.prd?gclid=CNzGqbLIssMCFUPJtAod1DAAGg&ecamp=SEAPLA195284_BQ&ef_id=VLXV9gAABOl8FNot:20150126210723:s

Could this small rise in height achieve a little more field above the roof line?

Haven't seen those before!

I had an image of a heavy timber frame to lug around the garden. That looks very light weight and stable - and a little bit cheaper than a 10" Newtonian

I'll give that a go - thanks, Charic.

[Charic]

......no problem matey, I've been after one for ages for my Dob, but they only do small here in Scotland??? I have to mail order it, and the postage costs more than the base for an Islands & Highlands postcode, even though I live in Moray?

I Think I need one with a top surface area to accommodate the base of my Dob which I believe is @52cm. make sure you get the right size, so that the Dob base  just rests securely on the Butt, otherwise some modifications may be required. I see the 'Butt' as an essential item for when away from base, snuggled up in a spooky forest with Deer running past, how do they do that in the dark,  hell of a scare. can they see me? I can't see them! The Butt just keeps the telescope out of the muck and long grass, vegetation. 

[DRT]

they only do small here in Scotland???

I'm Scottish. I know why they only encourage small water butts - it's because they fill up every day!

Do you ever travel down south? As far as Edinburgh? If so I could export one to there that you could collect when convenient.

[Polar Bear]

AS to your question I think the big fast newts are good for visual. Yes you will get some degradation of view towards the edges without a coma corrector but I think a bigger problem is choice of EP. Having said that I got this setup as a light bucket and can put up with the optical shortcomings.  

Fitting a 10" F4.7 OTA on a Skytee II did it for me. Comfortable and useful height for viewing around the ecliptic with the tripod at minimum. You could easily get another foot in height, and the Skytee with a counterweight handles the 16Kg load without issue. 

I can take more photos and measurements if you require them. 

Paul 

[DRT]

Paul,

That is exactly what I had in mind, thank you.

Are those 1.75" or 2" legs? I have both and it would be good to know if both were an option?

[Charic]

DRT...thanks for the offer. May already have found one on ebay( sensible postage this time?) Just got to clarify that their details are correct. Needing the 550mm top to accommodate the 52cm base. 

[John]

AS to your question I think the big fast newts are good for visual. Yes you will get some degradation of view towards the edges without a coma corrector but I think a bigger problem is choice of EP. Having said that I got this setup as a light bucket and can put up with the optical shortcomings.  

Fitting a 10" F4.7 OTA on a Skytee II did it for me. Comfortable and useful height for viewing around the ecliptic with the tripod at minimum. You could easily get another foot in height, and the Skytee with a counterweight handles the 16Kg load without issue. 

I can take more photos and measurements if you require them. 

Paul 

IMG_0564.JPG

Thats an excellent solution Paul

I note you have upgraded the dovetail clamp on the Skytee to an ADM one. Essential in my view, with a heavy scope on there. The standard Skytee clamps are not reliable under heavy loads IMHO.

[Polar Bear]

Hi Derek

they are 1.75" legs, all Skytees are fitted with these. It is the same tripod as the HEQ5. The head can be bought individually. 

With a 30Kg rating they are more than sufficient.  The standard dovetail saddles are not good and I would only trust them with a light scope. ADM saddles make a big difference but it all adds to the cost.

Paul 

[DRT]

I've already got a Giro-3 mount which takes 18kg each side so no problem there. It is sitting on 2" EQ5/6 legs and a 16" pillar so stability isn't the problem. It's great to hear you have tackled the problem successfully and I am sure my collection of TV and ES eyepieces will cope well enough.

Game on!

[Polar Bear]

I've already got a Giro-3 mount which takes 18kg each side so no problem there. It is sitting on 2" EQ5/6 legs and a 16" pillar so stability isn't the problem. It's great to hear you have tackled the problem successfully and I am sure my collection of TV and ES eyepieces will cope well enough.

Game on!

I wish you more success than me. The OTA / Mount / EP combination I have is great but the LP where I am is terrible and this combo is too big and heavy for a grab and go. I have just got back into visual and have obviously forgot why it was that 3 years ago I got a C8 and concentrated on the Moon and Planets. As this isn't a go-to mount and the sky is so washed out I spend more time looking for stuff than actually observing it. 

I am sure the Giro and the 250PDS will be a good combination providing your skies are better than mine.

Paul 

[happylimpet]

I have a 12" f/5 300p on an equatorial mount and its awesome visually (though i mostly image these days) and a 12" f.6 Dob, which is also awesome (and it visits the countryside).

There is no substitute for aperture. Do it.

[DRT]

I picked up a Skywatcher 250P from a nice man named Angus today for a very reasonable price. I popped it on the Giro III when I got home and it sits very well alongside my ST102 and doesn't seem to need and additional weight to balance it.

If the stars ever appear again I will report back on how it performs

[Polar Bear]

Welcome to the 'Big Newt on a Swivel Club' 

[DRT]

Welcome to the 'Big Newt on a Swivel Club' 

Thanks, but I think I also need a box to stand on to reach the eyepiece