Herschel wedge

Solar Array

Today allowed me to finally get my Solar array set up. After several attempts at balancing and positioning all the components and making modifications I was able to set up all 3 scopes in a balanced configuration.

Then using the Kendrick Solar finder on the central scope (Evostar 120) and setting the tracking to solar rate I then adjusted the alignment of the ST 102 and the PST, so that all 3 scopes showed full disk of sun in centre of field of view.

The idea is that:

the central scope will give white light images of the sun using a Herschel wedge with an ND3 filter.

the smaller ST102 refractor will give CaK images using a Herschel wedge without any filter and imaged with DMK41 mono ccd camera with Baader Calcium K filter fitted.

the PST will give H alpha images.

Today I was only using set up visually , to align scopes, so I used filtered Herschel wedge in the Evostar 120, a baader Solar film on front of ST 102 and the PST was used as normal. There were no sunspots visible and in H alpha a noticeable prominence at 4/5 o-clock position as registered by Roger this morning, no other prominences visible, nor was there much surface detail. No CaK detail as was not using camera, the sun was very variable , but there were enough bright spells this afternoon between 2 and 4pm to allow the alignment of all three scopes.

The mount was constructed with a piece of 10mm thick Aluminium bar 10cm wide and 35 cm long attached to upper side of lower vixen bar via two M6 bolts.

Two vixen bars were then attached to upper surface of Aluminium bar via M6 bolts, two sets of ADM mounting rings of suitable size were then clamped onto these vixen bars.

(ADM rings and vixen bars from First Light Optics.)

By adjusting screws in Rings I was able to align both scopes to get full disk in centre field of view, to remove scopes the top adjusting screw only in each ring is taken out, so when  scopes placed back in , tightening this screw only should put them back in aligned position, all bar a slight tweak.

To ensure the system was balanced about the axis running along the length of the Evostar, extra masses were added under the PST, these were attached via an M10 bolt with head removed and centre tapped with M6 thread, then attached to vixen bar with M6 screw head bolt through Vixen bar and M10 bolt to hold masses in place., this can be seen on photo below with scopes removed from rings.

By experiment on table top , approx. 1.5Kg was required on PST side to balance rig, brought 4 small masses from Astro Buy & sell, and drilled out centres to fit bolt. All we want now are some clear skies and sunspots!!

Thanks to Lee for advice on design and initial drilling and tapping of holes / threads.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Comparison of Visible and CaK images of sunspots. (6th Oct2017)

Below are 4 pairs of images of sunspots 2683 (large one) and 2682 ( smaller one , only in first two images) taken on 6/10/17. No H alpha was taken as at the end of this sequence high  cirrus stopped any further imaging, in fact last CaK shot is diminished by the entrance of the high cirrus. Experiences of using CaK so far suggests that it brings out more detail in the faculae (bright spots) around sunspots , these are linked to the intense magnetic fields associated with sunspots. The other noticeable effect with CaK is the longer exposure time required, discussion at the IAS suggested that since the filter is double stacked, it requires a Herschel wedge without a ND.3 neutral density filter as supplied by Astrograph ( it’s on my list for Santa!!) , also choice of barlows can be crucial depending on coatings, will see what happens when I’ve tried the new Herschel wedge.

The images are laterally inverted, I haven’t flipped them.

Images are below and are self explanatory.

Pete H

Sun in a new Light – Cak

Using recently acquired skywatcher ST102 refractor, see above with collapsible dark box and shroud.  Along with a Baader CaK double stacked filter 390 – 398 nm covering both CaK 393.7 nm and CaH 396.85 nm I managed to image the sun in Ca k.

The filter was attached to a DMK41 mono CCD camera with a x0.5 focal reducer to enable whole disc imaging.

 

The CaK filter needs an energy rejection system to be used on scope, it comes packaged with 3.8 OD Baader film, but a Herschel wedge can also be used.

Other CaK systems like those available from Lunt contain both Cak filter and energy rejection system, hence the cost.

I missed the early morning activity recorded by Nick and Roger and by this afternoon there was little prominence activity according to Gong, so I just concentrated on Sunspot AR2670, imaging using CaK filter and the Baader 590nm Contiuum filter.

Whole disk in White light, continuum filter.

Whole disk in CaK, showing Plages

Colourised CaK whole disk.

 

Left white light image without x0.5 focal reducer.

Centre CaK without focal reducer.

 

 

Below colorised Cak

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

With x2 Barlow (below), smaller image white light. Trying to dodge between clouds meant that the sun was getting lower during the session and subsequently I was imaging over my neighbours roof and the garage roof, started to get lots of atmospheric wobble. However I was reasonably pleased that different detail could be imaged with the CaK filter, couldn’t take H alpha (656.78nm) at same time as I’d used the vixen rail I normally attach it to, to mount the ST102 on the HEQ5. Compare the rese CaK images with Rogers H alpha.

The white light image shows what is happening on surface of suns photosphere, the observeable surface at 5500k, H alpha shows what  is happening in the chromosphere, the layer above the photosphere where the temperature rises to 50000K at its upper level. CaK images show what is occurring between the upper photosphere and lower chromosphere.

At 393.37 nm CaK is not visible to eye , in fact there is a lot of UV being passed, not good for the eyes, so this filter is for imaging purposes only.

Future activity will compare Herschel wedge / Baader film combinations with CaK filter and comparison with H alpha images from Coronado PST.

Pete H


Solar Observations 26th May 2017

Not only was the evening observing good at the last RAG meeting, earlier in the day afforded the opportunity for some Solar observing. Although we are approaching the next Solar minima, there was a sunspot group present and some prominences were visible. The prominences were more of the spicule type that are very short lived and at the end of the imaging session the prominences recorded had disappeared, checking on GONG time-lapse  these prominences appeared and disappeared.

First 3 images taken in H alpha using Coronado PST and DMK41 mono CCD, best 50 of 1000 frames stacked in Autostakkert, wavelets in Registax 6, Photoshop CS^ for combination of disc and prominences, colourising and final tweak.

1.Full disc and prominences. 2 Close up of sunspot x2Barlow 3, Close up of prominence xBarlow.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

 

 

 

 

 

 

 

 

 

Next two images are in White light, using 120mm Evostar refractor, with Lunt Herschel wedge imaged with DMK41 with Baader continuum filter. Best 50% of 1000 frames stacked in Auto stakkert, wavelets in Registax 6 and finished in Photoshop CS6

1. Sunspot 2,sunspot x2 Barlow