SW Startravel 120 mm chromatic Aberration

[Sirius Starwatcher]

The link below shows where I am coming from.

http://stargazerslounge.com/topic/230380-second-scope-assistance-please/

http://stargazerslounge.com/topic/234106-it-could-be-a-long-wait/

Having researched awhile now, I am still undecided on the scope I want. Any one owning the ST 120mm, can you advise me on the chromatic Aberration of this scope, how bad is it / Can I reduce it with accessories.I ask because I am now looking at the Skymax 127. The pararmeters at the original post still stand. I can afford to up my spend for the right telescope. Many thanks for reading

[Moonshane]

I have the 120mm f5 SW scope and use it mainly as a white light solar scope at which it excels with the Lunt wedge. It produces amazingly detailed views of the sun. I also use it occasionally as a grab and go night time scope and it's also pretty good. My mount of choice is the Giro 3 but it would work OK on a AZ4 which I have had previously - the Giro 3 is better though. It's on a steel 2" tripod.

The scope works really well as a wide field lower power scope and for objects other than the moon and brighter planets it is very good. Views of the brighter Messiers are bright and contrasty for the aperture and recently comet Lovejoy was best in this scope.

On the moon there is quite a lot of CA and also on Jupiter. I'd say between 100-150x is the max magnification feasible even on the moon. You may improve matters on the brighter objects by making a removable aperture ring to reduce to 100mm. I would not really be looking at these objects when on holiday though as to me at least, the point of taking a smaller scope somewhere darker is that you see things not visible from home. Therefore I'd be sticking to fainter objects, clusters, galaxies and nebulae that are not really visible at home and would be revealed from a dark sky and 120mm of aperture. On these sorts of objects this scope excels. I use a 2" diagonal and my 26mm Nagler and it's a joy.

[Moonshane]

http://www.astrobuysell.com/uk/propview.php?view=92509 the £100 but not a bad deal.

[Sirius Starwatcher]

I have the 120mm f5 SW scope and use it mainly as a white light solar scope at which it excels with the Lunt wedge. It produces amazingly detailed views of the sun. I also use it occasionally as a grab and go night time scope and it's also pretty good. My mount of choice is the Giro 3 but it would work OK on a AZ4 which I have had previously - the Giro 3 is better though. It's on a steel 2" tripod.

The scope works really well as a wide field lower power scope and for objects other than the moon and brighter planets it is very good. Views of the brighter Messiers are bright and contrasty for the aperture and recently comet Lovejoy was best in this scope.

On the moon there is quite a lot of CA and also on Jupiter. I'd say between 100-150x is the max magnification feasible even on the moon. You may improve matters on the brighter objects by making a removable aperture ring to reduce to 100mm. I would not really be looking at these objects when on holiday though as to me at least, the point of taking a smaller scope somewhere darker is that you see things not visible from home. Therefore I'd be sticking to fainter objects, clusters, galaxies and nebulae that are not really visible at home and would be revealed from a dark sky and 120mm of aperture. On these sorts of objects this scope excels. I use a 2" diagonal and my 26mm Nagler and it's a joy.

[Sirius Starwatcher]

If I can improve the viewing by reducing the apperture to 100mm would it not make sense to purchase the 100 and not the 120mm ?

[Moonshane]

The CA is only an issue on brighter objects so if you buy the 120mm and make a mask, you can add it for brighter objects (e.g. if CA bugs you and you use it for grab and go on the moon at home) and then remove it for the benefit of full aperture on the fainter objects at home and away.

[Moonshane]

of the two I'd go for the 120mm every time but I'd not be that happy with just the 120mm as my only scope. you have another option but make no mistake, neither is really optimal for solar system objects. I also think both have a little spherical aberration or field curvature. e.g. the moon goes a little egg shaped at the edge of field.

all round a f5 150mm newt would be better if space allows.

[Starlight 1]

This post go back to 2012 ,this was with a SW st80 but the same thing this was the post for the best filter at the time.

#4

jgs001

Posted 17 May 2012 - 04:11 PM

Hyper Giant

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I know they're for Baader filters, not Siruis, but it might be worth a look at

http://stargazerslou...ead.php?t=67599

The Baader Fringe Killer, is I think the equivalent of the MV1, I guess the Semi APO is like the MV20. I've no idea if the Baader filters have an IR/UV cut filter or not...

For me, I'd be probably using the MV20 to get a more natural view, but you may need an IR filter also.

[John]

Filters will reduce the CA but it will still be quite apparent and the other abberations that Shane mentions will still be present.

Personally I think these fast achromat refractors are best played to their strengths which are low to medium power, wide field observing.

If thats the principle use you have in mind they are great fun

[DRT]

http://www.astrobuysell.com/uk/propview.php?view=92509 the £100 but not a bad deal.

I'm glad to hear that, Shane, especially since I bought that one yesterday morning before reading this thread

[Bobby1970]

You could always add a semi app type filter. Which is what i recently did with my ST102. It certainly improves things but just don't expect miracles. Try and get one second hand rather than shelling out full price for one. I love my ST102 and still use it regularly. Nice and portable no maintenance issues, good for solar with the right filter obviously. I have a 127mm Mak for planetary stuff and use the ST102 for widefield observing.